Do you see any error messages? It may be that the Cosmote servers don't support the minimum TLS version required by TB 78, which would result in a 'peer using unsupported version of security protocol' error.

What is the antivirus app?

I was messing around with different settings and realized that i was able to send emails from the beggining, but didn't know it. The problem was at receiving them and no it didn't show any error messages. Today i changed the setting "connection security" from SSL/TLS to None and it works, i am receiving new mails. So i guess i am going to leave it as it is. I have Avira antivirus but i don't think it has anything to do with it.

Thanks.

You are certainly not alone. I have the exact problem as you do and there are other users reporting same issues as well on the forum. Was running 68.12.0 fine but after updating to 78.2.2, Thunderbird would no longer download new emails. Status bar showed it is online, when clicked on Get Messages, the status bar displayed "Connected to" my email server but somehow the connect was reset and not proceeding to say "Host contacted, sending login information" or "Checking inbox for new messages".

Now I've installed an older version Thunderbird 68.9.0 (32-bit version as I'm running Win10 32-bit OS) from the Thunderbird releases download page. Needed to create a new profile as my original profile cannot be re-used in an older version after running 78.2.2. At least I'm able to download new emails from my ISP email server again with 68.9.0.

I can get by downloading emails for now but hopefully, someone can provide a solution or further 78.x updates will fix the problem.

Coming back for update. Cosmote suggests to use imap settings for emails. Well the imap settings with the new version 78.2.2 don't work. I deleted my account (backing up everything first) and added it again, only this time i used POP3 settings and now is working fine at the moment. Sending and receiving without problem.

Thunderbird 78 requires that the server have TLS V1.2 or later to connect using ssl/TLS connection security.

Setting the connection security to none will work with most ISP's while you wait for them to update to TLS V1.2 more than a decade after it was released.

There is a change to Thunderbird that can be made to force it to accept the obsolete and broken TLS versions, but really none is just as secure as broken and you are aware that it is not optimal if you use none.

The report I got on the cosmos IMAP mail server suggests that the only encryption offered is so flawed it has known exploits. eg Poodle. See https://en.wikipedia.org/wiki/POODLE

Hi noulask, I tried svlad2009's suggestion to change the security.tls.version.min from the default value 3 to 1 in TB 78.2.2 and it worked, so I can download new emails in TB 78.2.2 again. This is actually the first time I used the Config Editor in TB :) Here are the steps:

From the menu bar, select: Tools > Options. Under General tab, scroll to the bottom and select: Config Editor... then click I accept the risks! Search for the line "security.tls.version.min". Click or double click on this line and enter new integral value of 1 to replace 3 (or 2) and click OK and close the box to complete. Then try to check your email again! Hopefully it will work for your too! Cheers!