this was hard to find, but it is
here
in THE WHOLE SCOOP ON THE CONFIGURATION FILE.
relevant excerpt:
- a
- Run Extended SMTP (ESMTP) protocol (defined in RFCs 1651, 1652, and 1653).
This flag defaults on if the SMTP greeting message includes the word
ESMTP.
- A
- Look up the user part of the address in the alias database.
Normally this is only set for local mailers.
- b
- Force a blank line on the end of a message.
This is intended to work around some stupid versions of
/bin/mail
that require a blank line, but do not provide it themselves.
It would not normally be used on network mail.
- c
- Do not include comments in addresses.
This should only be used if you have to work around
a remote mailer that gets confused by comments.
This strips addresses of the form
Phrase or
address (Comment) down to just
address.
- C
- If mail is
received from a mailer with this flag set,
any addresses in the header that do not have an at sign
(
@) after being rewritten by ruleset three
will have the
@domain clause from the sender envelope address
tacked on.
This allows mail with headers of the form:
- From: usera@hosta
To: userb@hostb, userc
to be rewritten as:
- From: usera@hosta
To: userb@hostb, userc@hosta
automatically.
However, it doesn't really work reliably.
- d
- Do not include angle brackets around route-address syntax addresses.
This is useful on mailers that are going to pass addresses to a shell
that might interpret angle brackets as I/O redirection.
- D*
- This mailer wants a
Date: header line.
- e
- This mailer is expensive to connect to,
so try to avoid connecting normally;
any necessary connection will occur during a queue run.
- E
- Escape lines beginning with
From in the message with a `>' sign.
- f
- The mailer wants a
-f
from flag,
but only if this is a network forward operation
(i.e.,
the mailer will give an error
if the executing user
does not have special permissions).
- F*
- This mailer wants a
From: header line.
- g
- Normally,
sendmail sends internally generated email (e.g., error messages)
using the null return address
as required by RFC 1123.
However, some mailers don't accept a null return address.
If necessary,
you can set the
g flag to prevent
sendmail from obeying the standards;
error messages will be sent as from the MAILER-DAEMON
(actually, the value of the
$n macro).
- h
- Upper case should be preserved in host names
for this mailer.
- i
- Do User Database rewriting on envelope sender address.
- I
- This mailer will be speaking SMTP
to another
sendmail --
as such it can use special protocol features.
This option is not required
(i.e.,
if this option is omitted the transmission will still operate successfully,
although perhaps not as efficiently as possible).
- j
- Do User Database rewriting on recipients as well as senders.
- k
- Normally when
sendmail connects to a host via SMTP,
it checks to make sure that this isn't accidently the same host name
as might happen if
sendmail is misconfigured or if a long-haul network interface is set in loopback mode.
This flag disables the loopback check.
It should only be used under very unusual circumstances.
- K
- Currently unimplemented.
Reserved for chunking.
- l
- This mailer is local
(i.e.,
final delivery will be performed).
- L
- Limit the line lengths as specified in RFC821.
This deprecated option should be replaced by the
L= mail declaration.
For historic reasons, the
L flag also sets the
7 flag.
- m
- This mailer can send to multiple users
on the same host
in one transaction.
When a
$u macro occurs in the
argv part of the mailer definition,
that field will be repeated as necessary
for all qualifying users.
- M*
- This mailer wants a
Message-Id: header line.
- n
- Do not insert a UNIX-style
From line on the front of the message.
- o
- Always run as the owner of the recipient mailbox.
Normally
sendmail runs as the sender for locally generated mail
or as
daemon (actually, the user specified in the
u option)
when delivering network mail.
The normal behaviour is required by most local mailers,
which will not allow the envelope sender address
to be set unless the mailer is running as daemon.
This flag is ignored if the
S flag is set.
- p
- Use the route-addr style reverse-path in the SMTP
MAIL FROM: command
rather than just the return address;
although this is required in RFC821 section 3.1,
many hosts do not process reverse-paths properly.
Reverse-paths are officially discouraged by RFC 1123.
- P*
- This mailer wants a
Return-Path: line.
- q
- When an address that resolves to this mailer is verified
(SMTP VRFY command),
generate 250 responses instead of 252 responses.
This will imply that the address is local.
- r
- Same as
f, but sends a
-r flag.
- R
- Open SMTP connections from a
secure port.
Secure ports aren't
(secure, that is)
except on UNIX machines,
so it is unclear that this adds anything.
- s
- Strip quote characters (" and \e) off of the address
before calling the mailer.
- S
- Don't reset the userid
before calling the mailer.
This would be used in a secure environment
where
sendmail ran as root.
This could be used to avoid forged addresses.
If the
U= field is also specified,
this flag causes the user id to always be set to that user and group
(instead of leaving it as root).
- u
- Upper case should be preserved in user names
for this mailer.
- U
- This mailer wants UUCP-style
From lines with the ugly
remote from on the end.
- w
- The user must have a valid account on this machine,
i.e.,
getpwnam
must succeed.
If not,
the mail is bounced.
This is required to get
.forward capability.
- x*
- This mailer wants a
Full-Name: header line.
- X
- This mailer want to use the hidden dot algorithm
as specified in RFC821;
basically,
any line beginning with a dot
will have an extra dot prepended
(to be stripped at the other end).
This insures that lines in the message containing a dot
will not terminate the message prematurely.
- 0
- Don't look up MX records for hosts sent via SMTP.
- 3
- Extend the list of characters converted to =XX notation
when converting to Quoted-Printable
to include those that don't map cleanly between ASCII and EBCDIC.
Useful if you have IBM mainframes on site.
- 5
- If no aliases are found for this address,
pass the address through ruleset 5 for possible alternate resolution.
This is intended to forward the mail to an alternate delivery spot.
- 7
- Strip all output to seven bits.
This is the default if the
L flag is set.
Note that clearing this option is not
sufficient to get full eight bit data passed through
sendmail. If the
7 option is set, this is essentially always set,
since the eighth bit was stripped on input.
Note that this option will only impact messages
that didn't have 8->7 bit MIME conversions performed.
- 8
- If set,
it is acceptable to send eight bit data to this mailer;
the usual attempt to do 8->7 bit MIME conversions will be bypassed.
- 9
- If set,
do
limited 7->8 bit MIME conversions.
These conversions are limited to text/plain data.
- :
- Check addresses to see if they begin
:include:; if they do, convert them to the
*include* mailer.
- |
- Check addresses to see if they begin with a `|';
if they do, convert them to the
prog mailer.
- /
- Check addresses to see if they begin with a `/';
if they do, convert them to the
*file* mailer.
- @
- Look up addresses in the user database.