Can't Send Emails in Thunderbird on Win 10

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by stfextcom » Sun Jan 10, 2021 5:03 pm

I use Thunderbird and am upgrading to Win 10. I unable to send any emails! I have checked Server and Outgoing settings several times with tech support and everything seems fine. can log in and see the inbox but sending asks to retype the password and it will not connect to the outgoing server. (I can send in the Web interface)

My Win 8.1 machine works fine on my main email account but it seems about the time of the Tbird upgrade to 78.6.0 some accounts have the same problem. My posting to the Tbird forum has not helped but I hear that many Sonic accounts use Tbird so I thought someone here might know what to check. Any assistance or resources would be much appreciated.

Thanks in advance,

by virtualmike » Sun Jan 10, 2021 6:45 pm
I'm using T-bird 78.6.0 and I'm able to send with no problems. Here are my settings.

About a month ago, I started having some issues (T-Bird 78.4.0), because my anti-virus (Eset NOD32) made some changes to the way it handled SSL connections. Once I got that ironed out, I haven't had any issues. Is it possible your anti-virus isn't cooperating? Can you turn off its email scanning temporarily?
by syntaxsid1 » Mon Jan 11, 2021 11:06 am
VirtualMike may be spot on. The trouble may be when using SSL. I would suggest trying no SSL when setting it up to see if this helps as it may be an issue with the encryption protocol. When setting up the account on Thunderbird again, make sure the outgoing server name is "" and use port 587 and NOT 465 to see if this helps. Be sure to uncheck or remove SSL as the option as well. Usually this is the case if you KNOW your password is correct and it keeps saying it's wrong or "can't deliver". Let us know if this helps.

Kind Regards,

Jeff M.

Your antivirus interactions may indeed be the culprit also Definitely turn off any "email scanning" or virus checks for email specifically to see if that helps.
Jeff M. with Community Escalations @ Sonic
by stfextcom » Tue Jan 12, 2021 7:23 pm

I Have:

1) Disabled Sophos and the problem did not change (Jeff - Does this cover "remove SSL option"?)
2) Checked using port 587 as directed
3) Checked server name is ""
4) Tried "STARTTLS" as connection security, no change

I can still send emails from my account on the Win 8.1 machine every time. I'm stumped, any place else you can think to look? There must be lots of folks using Win 10 with Tbird, Tech support said they had heard of problems but did not follow the resolution. This has to be something simple?

Thanks Mike and Jeff, and anyone else who can think of a something else to check or another reference to consult.


by stfextcom » Thu Jan 14, 2021 4:51 pm
Note to Jeff:

Regarding this comment:

'Be sure to uncheck or remove SSL as the option as well. Usually this is the case if you KNOW your password is correct and it keeps saying it's wrong or "can't deliver." ''

Would you please point out from where to remove SSL, I have not seen it. As to the PW, I regularly login with it but the first send it asks for a repeat where it is not accepted and I have repeated it many times..

I have an unbelievable amount of time into this for something this simple but I have 2 fresh installs of Win 10 Pro that both have the same problem. It is hard to believe that I made the same mistake twice.

I bet if there is a Thunderbird expert there, this could take just a few minutes to discover.

Thanks again for everyone's efforts,

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