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