F=@

User can be User Database key V8.7 and later

When V8.7 or above sendmail has been compiled with User Database support (userdb on page 942) you can specify this delivery agent flag for a delivery agent and thereby cause that delivery agent to perform a User Database lookup for each address it handles. For sender header and envelope addresses, a User Database mailname keyword is used to perform reverse aliasing. For recipient envelope addresses, a User Database maildrop keyword is used to perform additional forward aliasing.[290] Note that any address with a leading @ character (in the $: part of the triple returned by the parse rule set 0) causes User Database lookups to be skipped. Also note that the absence of an F=i delivery agent flag (F=i on page 772) suppresses User Database rewriting of the envelope sender.

If the F=@ delivery agent flag is present, the delivery agent will try to use the User Database. If the F=@ delivery agent flag is absent, all User Database lookups are skipped. In general, this delivery agent flag should be present for the local and local-clone delivery agents but absent for all others. In configuration files prior to version 6 (The V Configuration Command on page 580), this delivery agent flag is automatically set for the local delivery agent.

[290] * See F=j (F=j on page 773) for User Database lookups of header recipient addresses.

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