IMAP account can't save any email with attachment

Hi,

I'm getting a curious problem where if I write a draft without an attachment and click save. It'll work without any issue at all.

But if I do the same, then attach a file to the email, it'll sit there for a couple of minutes before timing out (I'm using thunderbird), it'll eventually give you a message saying

"Your draft message was not copied to your drafts folder (Drafts) due to network or file access errors."

I've got all of dovecots verbose logging turned on. I'm using dovecot as a submission server through to the postfix server to do the actual sending. All the logging is turned on there too. But I can't figure out what the problem is.

Is there anything I can look for in the logs that will help me out?

chris