SMM:08-56
Sendmail Installation and Operation Guide
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 deliv-
ering network mail. The normal behavior 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 RFC 821 section 3.1, many hosts do not process
reverse-paths properly. Rev erse-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. sendmail must be running as root to
be able to use this flag.
s
Strip quote characters (" and \) 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 effective user id to be set to that user.
u
Upper case should be preserved in user names for this mailer. Standards require preservation
of case in the local part of addresses, except for those address for which your system accepts
responsibility. RFC 2142 provides a long list of addresses which should be case insensitive. If
you use this flag, you may be violating RFC 2142. Note that postmaster is always treated as a
case insensitive address regardless of this flag.
U
This mailer wants UUCP-style "From" lines with the ugly "remote from <host>" 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. See also the MailBoxDatabase option. This is required to get ".forward"
capability.
W
Ignore long term host status information (see Section "Persistent Host Status Information").
x This mailer wants a "Full-Name:" header line.
X
This mailer wants to use the hidden dot algorithm as specified in RFC 821; 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.
z
Run Local Mail Transfer Protocol (LMTP) between sendmail and the local mailer. This is a
variant on SMTP defined in RFC 2033 that is specifically designed for delivery to a local mail-
box.
Z
Apply DialDelay (if set) to this mailer.
0
Don't look up MX records for hosts sent via SMTP/LMTP. Do not apply FallbackMXhost
either.
1
Don't send null characters ('\0') to this mailer.
2
Don't use ESMTP even if offered; this is useful for broken systems that offer ESMTP but fail
on EHLO (without recovering when HELO is tried next).
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.