This took me a bit of Googling to figure out. In order to get Postfix and Cyrus saslauthd to work nicely together using “[email protected]” username format, in /etc/sysconfig/saslauthd add the following flag at the bottom:
# Additional flags to pass to saslauthd on the command line. See saslauthd(8)
# for the list of accepted flags.
FLAGS=-r
Man page for this flag:
-r Combine the realm with the login (with an â@â sign in between). e.g. login:
“foo” realm: “bar” will get passed as login: “[email protected]”. Note that the realm
will still be passed, which may lead to unexpected behavior.