Chapter 20. The M (Mail Delivery Agent) Configuration Command

Other than relaying mail via SMTP or LMTP, the sendmail program does not perform the actual delivery of mail.[25] Instead, it calls other programs (called mail delivery agents [26]) to perform that service. Because the mechanics of delivery can vary widely from delivery agent to delivery agent, sendmail needs a great deal of information about each one. The sendmail M configuration command defines a mail delivery agent and provides the information that sendmail needs.

What’s New with V8.13

V8.13 sendmail has made four changes regarding delivery agents, three of which are described here and two of which are described in the specified sections:

  • The #error agent can now return a $@ quarantine with a reason (Section 11.1.2.6 [V8.13]).

  • Connections caching for the LPC delivery agent (Section 6.1 [V8.13]) is now provided.

  • The new F=B delivery agent flag strips all leading backslashes (Section 20.1.1 [V8.13])

  • The F=f flag has been removed from the defaults for local_lmtp (Section 20.1.2 [V8.13])

  • The new F=W delivery agent flag causes persistent host status to be ignored for an individual delivery agent (Section 20.1.3 [V8.13])

New F=B Delivery Agent Flag

The F=s (20.8.43[3ed]) delivery agent flag causes sendmail to dequote the recipient’s address before passing it to the selected delivery agent. Dequoting causes all quotation marks (“) and all leading backslashes (\) to be removed. But when a lighter touch is needed, you may use ...

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