399 lines
14 KiB
Plaintext
399 lines
14 KiB
Plaintext
SUMMARY OF CHANGES BETWEEN SENDMAIL V5 and V8
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The following is a summary of the changes between the last commonly
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available version of sendmail from Berkeley (5.67) and the latest
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version (8.6). I can't guarantee that it is complete.
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Many of these are ideas that had been tried in IDA, albeit many of
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them with a more general syntax.
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Connection Caching
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Instead of closing SMTP connections immediately, open connections are
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cached for possible future use. There is a limit to the number of
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simultaneous open connections and the idle time of any individual
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connection.
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This is of best help during queue processing (since there is the
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potential of many different messages going to one site), although
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it can also help when processing MX records which aren't handled
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by MX Piggybacking.
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MX Piggybacking
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If two hosts with different names in a single message happen to
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have the same set of MX hosts, they can be sent in the same
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transaction. Version 8 notices this and tries to batch the messages.
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For example, if two sites ``foo.com'' and ``bar.com'' are both
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served by UUNET, they will have the same set of MX hosts and will
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be sent in one transaction. UUNET will then split the message
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and send it to the two individual hosts.
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RFC 1123 Changes
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A number of changes have been made to make sendmail ``conditionally
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compliant'' (that is, it satisfies all of the MUST clauses and most
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but not all of the SHOULD clauses in RFC 1123).
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The major areas of change are (numbers are RFC 1123 section numbers):
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5.2.7 Response to RCPT command is fast. Previously, sendmail
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expanded all aliases as far as it could -- this could
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take a very long time, particularly if there were
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name server delays. Version 8 only checks for the
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existence of an alias and does the expansion later.
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5.2.8 Numeric IP addresses are logged in Received: lines.
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This helps tracing spoofed messages.
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5.2.17 Self domain literal is properly handled. Previously,
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if someone sent to user@[a.b.c.d], where a.b.c.d is
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your IP address, the mail would probably be rejected.
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Version 8 special cases these addresses.
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5.3.2 Better control over individual timeouts. RFC 821 specified
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no timeouts. Older versions of sendmail had a single
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timeout, typically set to two hours. Version 8 allows
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the configuration file to set timeouts for various
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SMTP commands individually.
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5.3.3 Error messages are sent as From:<>. This was urged by
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RFC 821 and reiterated by RFC 1123, but older versions
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of sendmail never really did it properly. Version 8
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does. However, some systems cannot handle this
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perfectly legal address; if necessary, you can create
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a special mailer that uses the `g' flag to disable this.
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5.3.3 Error messages are never sent to <>. Previously,
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sendmail was happy to send responses-to-responses which
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sometimes resulted in responses-to-responses-to-responses
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which resulted in .... you get the idea.
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5.3.3 Route-addrs (the ugly ``<@hosta,@hostb:user@hostc>''
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syntax) are pruned. RFC 821 urged the use of this
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bletcherous syntax. RFC 1123 has seen the light and
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officially deprecates them, further urging that you
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eliminate all but ``user@hostc'' should you receive
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one of these things. Version 8 is slightly more generous
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than the standards suggest; instead of stripping off all
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the route addressees, it only strips hosts off up to
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the one before the last one known to DNS, thus allowing
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you to have pseudo-hosts such as foo.BITNET. The 'R'
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option will turn this off.
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The areas in which sendmail is not ``unconditionally compliant'' are:
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5.2.6 Sendmail does do header munging.
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5.2.10 Sendmail doesn't always use the exact SMTP message
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text from RFC 821. This is a rather silly requirement.
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5.3.1.1 Sendmail doesn't guarantee only one connect for each
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host on queue runs. Connection caching gives you most
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of this, but it does not provide a guarantee.
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5.3.1.1 Sendmail doesn't always provide an adequate limit
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on concurrency. That is, there can be several
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independent sendmails running at once. My feeling
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is that doing an absolute limit would be a mistake
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(it might result in lost mail). However, if you use
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the XLA contributed software, most of this will be
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guaranteed (but I don't guarantee the guarantee).
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Extended SMTP Support
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Version 8 includes both sending and receiving support for Extended
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SMTP support as defined by RFC 1425 (basic) and RFC 1427 (SIZE);
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and limited support for RFC 1426 (BODY).
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Eight-Bit Clean
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Previous versions of sendmail used the 0200 bit for quoting. This
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version avoids that use. However, for compatibility with RFC 822,
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you can set option `7' to get seven bit stripping.
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Individual mailers can still produce seven bit out put using the
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`7' mailer flag.
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User Database
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The user database is an as-yet experimental attempt to provide
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unified large-site name support. We are installing it at Berkeley;
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future versions may show significant modifications.
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The user database allows you to map both incoming and outgoing
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addresses, much like IDA. However, the interface set is still
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better with IDA.
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Improved BIND Support
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The BIND support, particularly for MX records, had a number of
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annoying ``features'' which have been removed in this release. In
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particular, these more tightly bind (pun intended) the name server
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to sendmail, so that the name server resolution rules are incorporated
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directly into sendmail.
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The major change has been that the $[ ... $] operator didn't fully
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qualify names that were in DNS as A or MX records. Version 8 does
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this qualification.
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Keyed Files
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Generalized keyed files is an idea taken directly from IDA sendmail
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(albeit with a completely different implementation). They can be
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useful on large sites.
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Version 8 includes an "NIS" map class to support NIS/YP maps.
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Multi-Word Classes
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Classes can now be multiple words. For example,
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CShofmann.CS.Berkeley.EDU
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allows you to match the entire string ``hofmann.CS.Berkeley.EDU''
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using the single construct ``$=S''.
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Deferred Macro Expansion
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The $&x construct has been adopted from IDA.
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IDENT Protocol Support
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The IDENT protocol as defined in RFC 1413 is supported.
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Parsing Bug Fixes
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A number of small bugs having to do with things like backslash-escaped
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quotes inside of comments have been fixed.
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Separate Envelope/Header Processing
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Since the From: line is passed in separately from the envelope
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sender, these have both been made visible; the $g macro is set to
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the envelope sender during processing of mailer argument vectors
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and the header sender during processing of headers.
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It is also possible to specify separate per-mailer envelope and
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header processing. The SenderRWSet and RecipientRWset arguments
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for mailers can be specified as ``envelope/header'' to give different
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rewritings for envelope versus header addresses.
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Owner-List Propagates to Envelope
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When an alias has an associated owner-list name, that alias is used
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to change the envelope sender address. This will cause downstream
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errors to be returned to that owner.
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Dynamic Header Allocation
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The fixed size limit on header lines has been eliminated.
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New Command Line Flags
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The -B flag has been added to pass in body type information.
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The -p flag has been added to pass in protocol information.
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The -X flag has been added to allow logging of all protocol in and
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out of sendmail for debugging.
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Enhanced Command Line Flags
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The -q flag can limit limit a queue run to specific recipients,
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senders, or queue ids using -qRsubstring, -qSsubstring, or
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-qIsubstring respectively.
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New and Old Configuration Line Types
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The `T' (Trusted users) configuration line has been deleted. It
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will still be accepted but will be ignored.
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The `K' line has been added to declare database maps.
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The `V' line has been added to declare the configuration version
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level.
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The `M' (mailer) line takes a D= field to specify execution
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directory.
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New Options
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Several new options have been added, many to support new features,
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others to allow tuning that was previously available only by
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recompiling. Briefly:
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b Insist on a minimum number of disk blocks.
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C Delivery checkpoint interval. Checkpoint the queue (to avoid
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duplicate deliveries) every C addresses.
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E Default error message. This message (or the contents of the
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indicated file) are prepended to error messages.
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G Enable GECOS matching. If you can't find a local user name
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and this option is enabled, do a sequential scan of the passwd
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file to match against full names. Previously a compile option.
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h Maximum hop count. Previously this was compiled in.
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j Send errors in MIME-encapsulated format.
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J Forward file path. Where to search for .forward files -- defaults
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to $HOME/.forward.
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k Connection cache size. The total number of connections that will
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be kept open at any time.
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K Connection cache lifetime. The amount of time any connection
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will be permitted to sit idle.
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l Enable Errors-To: header. These headers violate RFC 1123;
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this option is included to provide back compatibility with
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old versions of sendmail.
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O Incoming daemon options (e.g., use alternate SMTP port).
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p Privacy options. These can be used to make your SMTP server
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less friendly.
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R Don't prune route-addrs. Normally, if version 8 sees an address
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like "<@hostA,@hostB:user@hostC>, sendmail will try to strip off
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as much as it can (up to user@hostC) as suggested by RFC 1123.
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This option disables that behaviour.
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U User database spec. This is still experimental.
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V Fallback ``MX'' host. This can be thought of as an MX host
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that applies to all addresses that has a very high preference
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value (that is, use it only if everything else fails).
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w If set, assume that if you are the best MX host for a host,
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you should send directly to that host. This is intended
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for compatibility with UIUC sendmail, and may have some
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use on firewalls.
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7 Do not run eight bit clean. Technically, you have to assert
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this option to be RFC 821 compatible.
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Extended Options
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The `r' (read timeout), `I' (use BIND), and `T' (queue timeout)
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options have been extended to pass in more information.
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The `A' (alias file) option has been extended to allow multiple
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alias files of different types.
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New Mailer Flags
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a Try to use ESMTP. It will fall back to SMTP if the initial
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EHLO packet is rejected.
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b Ensure a blank line at the end of messages. Useful on the
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*file* mailer.
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c Strip all comments from addresses; this should only be used as
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a last resort when dealing with cranky mailers.
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g Never use the null sender as the envelope sender, even when
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running SMTP. This violates RFC 1123.
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7 Strip all output to this mailer to 7 bits.
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New Pre-Defined Macros
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$k UUCP node name from uname(2).
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$m Domain part of our full hostname.
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$_ RFC 1413-provided sender address.
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New LHS Token
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Version 8 allows `$@' on the Left Hand Side of an `R' line to match
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zero tokens. This is intended to be used to match the null input.
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Bigger Defaults
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Version 8 allows up to 100 rulesets instead of 30. It is recommended
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that rulesets 0-9 be reserved for sendmail's dedicated use in future
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releases.
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The total number of MX records that can be used has been raised to
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20.
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The number of queued messages that can be handled at one time has
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been raised from 600 to 1000.
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Different Default Tuning Parameters
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Version 8 has changed the default parameters for tuning queue costs
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to make the number of recipients more important than the size of
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the message (for small messages). This is reasonable if you are
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connected with reasonably fast links.
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Auto-Quoting in Addresses
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Previously, the ``Full Name <email address>'' syntax would generate
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incorrect protocol output if ``Full Name'' had special characters
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such as dot. This version puts quotes around such names.
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Symbolic Names On Error Mailer
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Several names have been built in to the $@ portion of the $#error
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mailer. For example:
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$#error $@NOHOST $: Host unknown
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New Built-In Mailers
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Two new mailers, *file* and *include*, are included to define options
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when mailing to a file or a :include: file respectively. Previously
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these were overloaded on the local mailer.
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SMTP VRFY Doesn't Expand
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Previous versions of sendmail treated VRFY and EXPN the same. In
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this version, VRFY doesn't expand aliases or follow .forward files.
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As an optimization, if you run with your default delivery mode
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being queue-only, the RCPT command will also not chase aliases and
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.forward files. It will chase them when it processes the queue.
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This speeds up RCPT processing.
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[IPC] Mailers Allow Multiple Hosts
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When an address resolves to a mailer that has ``[IPC]'' as its
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``Path'', the $@ part (host name) can be a colon-separated list of
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hosts instead of a single hostname. This asks sendmail to search
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the list for the first entry that is available exactly as though
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it were an MX record. The intent is to route internal traffic
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through internal networks without publishing an MX record to the
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net. MX expansion is still done on the individual items.
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Aliases Extended
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The implementation has been merged with maps. Among other things,
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this supports multiple alias files and NIS-based aliases. For
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example:
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OA/etc/aliases,nis:mail.aliases
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Portability and Security Enhancements
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A number of internal changes have been made to enhance portability.
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Several fixes have been made to increase the paranoia factor.
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Miscellaneous Enhancements
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Sendmail writes a /etc/sendmail.pid file with the current process id
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and the current invocation flags.
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Two people using the same program (e.g., submit) are considered
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"different" so that duplicate elimination doesn't delete one of
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them. For example, two people forwarding their email to
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|submit will be treated as two recipients.
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The mailstats program prints mailer names and gets the location of
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the sendmail.st file from /etc/sendmail.cf.
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Many minor bugs have been fixed, such as handling of backslashes
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inside of quotes.
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A hook has been added to allow rewriting of local addresses after
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aliasing.
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