Try holding down ⇧ when clicking “Retry” in the error requester. That should generate a log file on the desktop which you can send to me (or add to this ticket). It'll help me figure out what the problem with the server is.

You may be able to get MailMate out of the current state (after doing the above) by deleting the message again in MailMate. The first time you delete a file then it is moved to the trash, the second time it is expunged. But MailMate probably considers it a message which needs to be uploaded now - since it disappeared from the Inbox before a successful move was made.

I fixed a problem with mailbox names recently which could explain the problem you have. Try holding down ⌥ when clicking “Check Now” in the Software Update preferences pane. You should get r3193 which should be a stable test version of MailMate.

I've carried out the following steps in the following order:

1 Log file generated - please find attached.

2 Upgraded to r3193. When I started this version, I first got a new error message:

"Connection problem for "Gradwell" account Cannot make a secure connection since STARTTLS is not advertised."

And it then gave me same error message as above, i.e. "Invalid characters in atom".

3 I quit MailMate. On the IMAP server, deleted the problem message in trash which MailMate created and expunged. Restarted MailMate - deleted the same message in trash (it turned a red colour) - and then took the account online.

4 MailMate seems to be working now.

5 I quit and restart MailMate - no "cannot make secure connection" error message anymore and no "invalid characters in atom" error message anymore.

Please find attached the original message which I had downloaded using Mailsmith (POP3), saved and deleted from the IMAP server. I've just zapped out my e-mail addresses (the message was sent to my me.com e-mail address which then redirected to another address) and my name.

If I can upload this message back to the IMAP server (I tried earlier using Mail to import it - it gave no error message but I got a blank new mailbox for some reason), I should be able to reproduce the problem. Failing that, I will get more e-mails from the sender (the airline BA's website) in the future.

In relation to explicitly setting 993 as the port, if I go to edit source, it shows:

• IMAP Server: pop3.gradwell.net
• User Name: xxx
• Port: not ticked but it does show "993" in grey
• Require SSL: ticked

I've ticked Port so assume that will prevent the error reoccurring.

I've had a look at the e-mails I've saved over the past few years and came up with the following similar message IDs:

Message-ID: <Sat Jul 04 00:58:14 BST 2009@blx09ba01>
Message-ID: <Fri May 18 04:01:34 BST 2012@blx09bd01>
Message-ID: <Mon Dec 31 23:30:50 GMT 2012@blx09bd01>

(being e-mails sent by certain sender(s) in ba.com but not all of them - the rest look normal)

I don't know why the latest message ID seems to contain quotes (the attached file above) but the above three in this comment don't.

The quotes were triggering the bug in MailMate:

Message-id: <"Thu Jan 10 04:00:50 GMT 2013"@blx09ba01>

The involved code wrongly assumed that quotes were never used in Message-IDs (not intentionally assumed).

A new test version is available in a few minutes (hold down ⌥ etc.).

And yes, when Port is ticked then 993 is the only port used.

Thanks - I've updated to r3198 and assume the problem should be solved now (but will let you know if otherwise).

(After I clicked install and relaunch for the update, it showed a blank window for the release notes and then MailMate crashed. I restarted, clicked to send crash reports to you and it seems OK now.)

Actually, no - if I start, quit, start, quit etc, it seems to crash every 2 or 3 starts.

I think it'll stop doing it if you disable crash reporting (General preferences pane).

I'll make sure to fix it soon and have a new version uploaded.

Thanks - disabled crash reporting and after starting/stopping a few times, it seems fine now - no more crashes.

A fixed version should be out in a few minutes. Sorry about the inconvenience.