Recipient delimiter and lmtp proxying

Hi,

I'm attempting to proxy lmtp using director to hash to the same backend as pop3/imap. My pop3/imap users are of the form:

username

and my lmtp users are of the form:

username@domain

Where domain is fairly redundant but does carry some useful information.

Now, I can proxy lmtp using user=%{username} and destuser=%{orig_user}, and this all appears to work correctly.

However, if I also try to pass a detail part through to the backend the lmtp users now take the form:

username+detail@domain

I can still use user=%{username} with recipient_delimiter = +, and the detail is correctly stripped, hashing works as expected.

However, I can no longer use destuser=%{orig_user}

Because recipient_delimiter = +, destuser becomes:

username@domain

And the detail part never reaches the backend.

There doesn't appear to be any variables suitable for the destuser expansion - %{auth_user} is unsupported (UNSUPPORTED_VARIABLE_auth_user) on override_fields and in the sql passdb driver.

Is there any "correct" way to do this? I can think of a couple of approaches that may work, but both seem like hacks to me:

1. Unset recipient_delimiter and manually strip the detail from the username in the passdb lookup.

2. Give up on passing detail via the login and instead pass the detail via a message header to sieve.

Any thoughts/suggestions?

-- Dave