enable_rset

Since: Version 2025.01.23-7273d2bc

The functionality described in this section requires version 2025.01.23-7273d2bc of KumoMTA, or a more recent version.

When set to true (the default is true), then kumo will issue an RSET SMTP command in between each message send on a connection.

The purpose of the RSET is a defensive measure, in case something unexpected and unaccounted for has left the connection in an unknown or undesirable state; it is used as a kind of "rollback" operation.

Disabling the use of RSET can be a micro-optimization to improve the efficiency of a connection, but when pipelining is in use, it will really be a marginal difference.

Perhaps the biggest reason for considering disabling this option is that certain Postfix load-shedding configurations will penalize the use of RSET, because it is considered to be a "junk" command. If you see a trace like this:

> RSET
> MAIL FROM:<sender@example.com>
> RCPT TO:<user@postfix.local>
< 250 2.0.0 Ok
< 421 4.7.0 mail.postfix.local Error: too many errors
> QUIT

then postfix on the destination is configured to penalize RSET and you may wish to disable its use.