It seems, that for us at least, this is caused by Spamassassin scanning larger (>1mb) mails containing uuencoded files, without mime attachment headers or anything.
But this only seems to happen sometimes or when spamd has been running for a little while, for if we feed an email that appears to have caused the memory problem into a restarted spamd, nothing happens. When spamd chokes on such a mail, it slowly but constantly increases its memory usage, eating up all the systems memory. We haven't been using a size-limit for exiscan/exim up till now, but that can hardly be the root cause of the problem, for why would need spamd gigabytes of memory when processing, let's say, a 10mb mail?
signature.asc
Description: This is a digitally signed message part
