All of a sudden (after used successfully since account creation) on 9th October, Thunderbird started erroring out when sending mail through daffodill.
At first, i thought it may be just a blip, but then when it asked for the password (saved in password manager so never asks) i thought it may be locked out, so reset it via Cpanel (where i can access the mail as normal).  Still no luck.

Sent a ticket in (#1612954) and was advised to check/change ports etc.  I had set the three accounts up on 587and they have always worked perfectly. Same results from office and home. I can telnet using my host name(s) so the ports are not being blocked (25, 26 and 587) but unable to send mail through daffodill.
I was promptly asked for a password for the server team to have a look so await their reply.

On looking through the forum, i notice lots of posts, some similar to my issue so kind of thinking ahead really but wondering if anyone is using google apps for mail purposes.  Is the standard edition free? It isn't clear on first look other than prompting you to use the premier account at £33 per user per year.

Been totally happy with LP and hope this is just a blip.

Great forum by the way! 

also a little suggestion make sure that your email connections are not consecutive and no more than three machines on the same IP is connecting. The limit may have been maxed out which I believe that is maybe 10 connections per IP on imap if I am not mistaken. If it is not request the maximum connection is set to see if this resolves your issue. Support and admins are always willing to do everything they can to resolve the issue.