I don't know if this is intended or not, but here it comes.

I have

• that copy plugin I was working on
• dovecot 1.0-test59
• thunderbird test client

My copy plugin looks for the X-DSPAM-Signature header line, and reports it to syslog as such: imap: we have a signature: "X-DSPAM-Signature: <sig>" where <sig> is replaced by what is found in the header line. This only happens when I copy in/out of the SPAM folder (which works fine).

Now, when a mail is copied from INBOX to SPAM that doesn't have the signature line, I return an error to the client saying the user can't do that copy since the signature line is necessary. I detect the condition of not having that signature line by checking like this: if (!(signature = mail->get_header(mail, "X-DSPAM-Signature")) { ... return error ... }

This works fine, error comes back.

Second try, copying a mail that has the header line: works.

So, lets do some code changes, disconnect and reconnect to reload the plugin. All of a sudden, copying mails that don't have the header line works too! Uhh? Lets go looking at syslog: imap: we have a signature: "X-DSPAM-Signature: "

The only rational explanation I could come up with is that dovecot caches the header line and somehow decided that since it knows about the X-DSPAM-Signature header line mails that don't contain it should have an empty version of it. Well, I can of course test for this (and I actually should anyway, an empty signature isn't useful to dspam), but I do think this is a bug since it makes distinguishing between empty and non-present header lines impossible.

Regards, johannes