You need to go into tools in Thunderbird, account settings, server settings and set up your POP3 server (incoming) and SMTP server settings to match your ISP server settings.

http://kb.mozillazine.org/Default_mail_client#Windows

I use TB and also have emails scanned by my AVP (AVG), so my settings will not help you. You also need to make it your "default" mail program for it to work.MelaR said

This seems to be a problem brought on by the latest version of TB. Can I roll-back to older version?

https://support.mozilla.org/en-US/kb/cannot-receive-messages

MelaR said

This seems to be a problem brought on by the latest version of TB. Can I roll-back to older version?

I have taken all the steps suggested in several responses to this type of question. None of them have helped. I am running a Windows 8.1 machine. Could that be the problem. Again, can I roll-back to the last version of TB?

I also have 8.1 Pro and haven't had that problem. You can try downloading an older version of TB, but I don't know whether your machine will allow the install? Pick your poison: <<Link deleted as it is not to a Thunderbird download in a Mozilla server >>

Old versions can be downloaded from the Mozilla FTP server if it is absolutely necessary. Not receiving mail is not necessary. EVER.

http://ftp.mozilla.org/pub/mozilla.org/thunderbird/releases/

Can you post your Troubleshooting Information? Help (Alt-H) - Troubleshooting Information

MelaR said

This seems to be a problem brought on by the latest version of TB. Can I roll-back to older version?

I have rolled back to an older version and it seems fine. Thanks for your suggestions!

@mdybluz I have removed the link from your reply as it does not meet the posting guidelines for this support site. ALL Mozilla versions are available on the FTP server from Mozilla. Packages downloaded elsewhere always contains the possibility that they have has unwanted nasties added. The last thing we want to do is point people to malware. It might be a remote issue with the site you posted ,but it is a possibility.

@MelaR In all probability it was your anti virus programs firewall component choking and dying on the updated version. Nortons in particular has a habit of blocking all mail after an upgrade until you modify the firewall or wait a week for Symantec to patch their definitions.

Downgrading is bad news and should never be undertaken in the long term. IMHO these 6 weekly updates are actually more important than the major releases as they patch security vulnerabilities. It is such a shame that products that are supposed to improve security such an anti virus are responsible for so much trouble when patches are installed.

MelaR said

This seems to be a problem brought on by the latest version of TB. Can I roll-back to older version?

Matt-

Thanks for your response.

The bit about all this that confused me was that TB downloaded one of my accounts just fine and the other would download sometimes, partially download at other times and freeze completely on occasion. I have turned off email filtering (I use Kaspersky Anti-Virus) and reloaded TB 38.0. So far things are fine, just keeping fingers crossed that something nasty doesn't come down through email.