Yosemite Mail Connections to the server on the default ports timed out.

Question

I have upgraded two machines to Yosemite and I am having huge problems with Mail. It works perfectly well with my .mac mail but it does not work with my xServer running OS X server 10.6.something. I have little triangles but the mail account and I get the message "Connections to the server “mailgate.cp-lighting.co.uk” on the default ports timed out."
Any machine running an older version of OS X has no problems connecting.
The machine running Yosemite all have the same problems, they all have the triangle, they all receive mail but if you read it or delete it, it re-appears as unread so I can receive 20 emails read then delete 6 and a few minutes later I have 20 unread emails again.
Worse mail in the outbox get stuck behind a queue so it takes ages to send any mail, if I look at activity viewer I can see processes constantly running "Moving Messages" , "Synchronizing Sent", "Updating Cache directory"[sent] , "changing flags" and finally "Updating Cache directory"[Inbox]
If I go to mail and preferences/accounts I cannot edit the incoming mail server it is greyed out. I wanted to change the domain nane for the ip address of the server to see if that made any difference but it is not possible. I don't understand what Apple have done it is a nightmare.
Is anyone else having these problems?

Answer 1

Yes, my husband has had this problem too with his IMAP email account. He is temporarily using Thunderbird, which is working better, but it is also reporting lost connections. Seems the issue is deeper within the networking or security services of Yosemite than the Mail app itself.