Is this a Pop or IMAP mail account ?

I'm assuming this is a 'Pop' mail account. Possibly a log jam is the cause.

Logon to webmail account using a browser and empty the 'Spam' folder. In Thunderbird click on 'Get Messages'.

If still stuck: In webmail account, delete the email which keeps being downloaded and also the oldest not downloaded email (read it first - then forward to yourself if required otherwise delete it). In Thunderbird click on 'Get Messages'.

Hi thanks for the advice, I tried those but it didnt work. The email which is causing the jam isn't coming through at all when I open the email via a web broswer

Bren150 said

Hi thanks for the advice, I tried those but it didnt work. The email which is causing the jam isn't coming through at all when I open the email via a web broswer

That is because it is in the web mail spam folder. If you can not find it, just disable you anti virus email scanner and then your mail will all download. It will be the actual "cause" of the problem.

Thanks Matt, that worked, much appreciated

Which option worked and what anti virus do you use? Just so I can update https://wiki.mozilla.org/Thunderbird:Testing:Antivirus_Related_Performance_Issues

I use AVG free, I turned off the 'Email shield', opened Thunderbird and the logjam of emails cleared, and the email which was the problem has gone. Thanks again