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smtp, etc.

Deliver using SMTP V8.1 and above

The five smtp delivery agents all use TCP to connect to other hosts. They are the smtp, esmtp, smtp8, dsmtp, and relay delivery agents. All five start with the same basic defaults, which are shown in Table 20-14. Support for all five is included in your mc configuration file like this:

MAILER(`smtp')

Table 20-14. Basic defaults for the smtp delivery agents

Macro

§

Default

SMTP_MAILER_ARGS

See this section

A=TCP $h

SMTP8_MAILER_ARGS

See this section

A=TCP $h

ESMTP_MAILER_ARGS

See this section

A=TCP $h

DSMTP_MAILER_ARGS

See this section

A=TCP $h

RELAY_MAILER_ARGS

See this section

A=TCP $h

SMTP_MAILER_CHARSET

C=

no C= default

RELAY_MAILER_CHARSET

C=

no C= default

none

E=

E=\r\n

SMTP_MAILER_FLAGS

See this section

F=mDFMuX smtp

SMTP_MAILER_FLAGS

See this section

F=mDFMuXa esmtp

SMTP_MAILER_FLAGS

See this section

F=mDFMuX8 smtp8

SMTP_MAILER_FLAGS

See this section

F=mDFMuXa% dsmtp

RELAY_MAILER_FLAGS

See this section

F=mDFMuXa8

none

L=

L=990 smtp, esmtp, smtp8, dsmtp

none

L=

L=2040 relay

SMTP_MAILER_MAX

See this section

no M= default all except relay

SMTP_MAILER_MAXMSGS

m=

no m= default

RELAY_MAILER_MAXMSGS

m=

no m= default

none

See this section

P=[IPC]

SMTP_MAILER_MAXRCPTS

r=

no r= default

none

R=

R=EnvToSMTP/HdrFromSMTP smtp, etc.

none

R=

R=MasqSMTP/MasqRelay relay

none

S=

S=EnvFromSMTP/HdrFromSMTP

none

T=

T=DNS/RFC822/SMTP

SMTP_MAILER_QGRP

Q=

no Q= default

SMTP8_MAILER_QGRP

Q=

no Q= default

ESMTP_MAILER_QGRP

Q=

no Q= default

DSMTP_MAILER_QGRP

Q=

no Q= default

RELAY_MAILER_QGRP

Q=

no Q= default

Note that each of the five smtp class delivery agents has it own way of specifying the A= delivery agent equate. That is so that you can run each on a different port if you so desire (See this section).

The smtp delivery agent

The smtp delivery agent speaks SMTP and has the F=mDFMuX delivery agent flags set by default (see Table 20-19 for the meaning of these delivery agent flags). It is a useful delivery agent if you connect to sites that disconnect when they are greeted with EHLO. Although such behavior violates standards, some hosts still run such broken software.

In general, esmtp is preferred over this smtp delivery agent.

The esmtp delivery agent

The esmtp delivery agent speaks ESMTP and has the F=mDFMuXa delivery agent flags set by default (see Table 20-19 for the meaning of these delivery agent flags). Note that these are the same delivery agent flags smtp uses, but with the F=a delivery agent flag added to enable ESMTP. This is the preferred delivery agent for delivery over networks.

The smtp8 delivery agent

The smtp8 delivery agent speaks SMTP and has the F=mDFMuX8 delivery agent flags set by default (see Table 20-19 for the meaning of these delivery agent flags). Note that these are the same delivery agent flags smtp uses, but with the F=8 delivery agent flag added to force sending 8-bit data over SMTP even if the receiving server doesn't support 8-bit MIME. You might prefer to use this delivery agent when forwarding to a central server that does not understand 8-bit MIME, but that can handle 8-bit data.

The dsmtp delivery agent

The dsmtp delivery agent speaks ESMTP and has the F=mDFMuXa% delivery agent flags set by default (see Table 20-19 for the meaning of these delivery agent flags). Note that these are the same delivery agent flags smtp uses, but with the F=a and F=% delivery agent flags added. The F=a delivery agent flag enables support for ESMTP. The F=% delivery agent flag causes all outbound email to be queued instead of sent, and not attempted on normal queue runs. This is extremely useful at a site that is polled only for email. A server with only dial-up accounts might be one example, or a server outside a firewall that is not allowed to push mail inward. With F=% delivery agent flag set, destination hosts need to request delivery with the ETRN command (Section 11.8.2.6). The local administrator can also cause delivery to occur with the -qI, -qR, or -qS command-line switches (Section 11.8.2.3).

The relay delivery agent

The relay delivery agent uses TCP to connect to other hosts. It speaks ESMTP and has the F=mDFMuXa8 delivery agent flags set by default (see Table 20-19 for the meaning of these delivery agent flags). Note that these are the same delivery agent flags smtp uses, but with the F=a and F=8 delivery agent flags added. The F=a delivery agent flag enables support for ESMTP. The F=8 delivery agent flag forces sending 8-bit data over SMTP even if the receiving server doesn't support 8-bit MIME. The relay delivery agent also uses an L= (L=) setting of 2040. It also does less header rewriting than the other SMTP-based mailers. This is the delivery agent chosen for forwarding mail to the SMART_HOST (Section 4.3.3.6), LUSER_RELAY (Section 4.5.6), BITNET_RELAY ($B), UUCP_RELAY (Section 4.5.8), DECNET_RELAY (Section 4.5.2), FAX_RELAY (Section 4.5.3), and MAIL_HUB (Section 4.5.7).

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