Hi list,
I set up dovecot as IMAP proxy using a master user to login into the backend and it works beautifully. 👍🏻 Next I set out to do LMTP proxying and I struggled (initially).

I got the log message:
Mar 17 11:23:44 mail postfix/lmtp[2665]: 99A3F219C8: to=<johnny@doe.com>, relay=10.15.1.2[10.15.1.2]:24, delay=5.1, delays=4.9/0.05/0.01/0.07, dsn=5.1.1, status=bounced (host 10.15.1.2[10.15.1.2] said: 550 5.1.1 <"johnny@doe.com*director"@mail.server.com> User doesn't exist: "johnny@doe.com*director"@mail.server.com (in reply to RCPT TO command))

My director's passdb setting looked like this:

passdb {
 driver = sql
 args = /etc/dovecot/sql/my-passdb.conf
 result_success = continue-ok
 result_failure = return-fail
 result_internalfail = return-fail
}

# Add director master user credentials if above succeeded
passdb {
 driver = static
 args = proxy=y starttls=any-cert \
     destuser=%u*director@example.com \
     pass=correcthorsebatterystaple \
     nopassword=y
 skip = unauthenticated
}

In the end I found that setting the `master` field instead of `destuser` solves the issue. It looks like LMTP does not know how to handle the master user separator although set. I this known/wanted behavior? Maybe this is something to mention on the wiki page, it took a while to figure this out...

Kind regards,
Dirk