Thunderbird access to comcast email no longer working

I've just changed my password, and it still doesn't work in Thunderbird. (I've verified that it does still work for webmail.) It still says "Login to server mail.comcast.net with username xxx failed." It always worked until now with mail.comcast.net as the server, but I've also tried pop.comcast.net, which also doesn't work. Everything worked fine last night, but not this morning.

@JeffG4  Please try these steps;

Remove and Re-enter Passwords:

Open Thunderbird and go to Tools > Options (or Preferences on macOS).
Navigate to Security > Passwords > Saved Passwords.
Click on Show Passwords, then find and remove the entries for your Comcast account.
Close and reopen Thunderbird. When prompted, enter your new password.
Verify Server Settings:

Ensure your incoming server is set to mail.comcast.net with port 995 and SSL/TLS encryption.
For the outgoing server, use smtp.comcast.net with port 465 or 587 and SSL/TLS encryption.
Check Authentication Method:

Go to Account Settings > Server Settings and ensure the Authentication method is set to Normal password.
Allow Third-Party Access:

Log in to your Comcast webmail and ensure that third-party access is enabled. This can sometimes be required for email clients like Thunderbird.
If these steps don't resolve the issue, you might want to try removing and re-adding your email account in Thunderbird, then contacting Thunderbird for further assistance. We generally do not troubleshoot third party programs.

I've now tried all that, and tried re-adding my email account, both as POP and IMAP--POP sends me to the Xfinity sign-in page and then errors out, telling me I don't have permission to login. IMAP just errors out locally, saying it is unable to log in at server. So ...

Thanks for your advice, even though this has to do with a third-party email program. I just figured, since Xfinity was doing something new with its email system, this might be a side effect of that.

@JeffG4​ I have the same issue. I can't use Thunderbird anymore with Comcast. Both pop3 and Imap fail. 

I was able to get it working in Outlook with Imap but not pop3. 

I don't know if there was a change in Thunderbird or Comcast.

I had the same issue. It was driving me nuts, but I found the issue. ARE YOU USING A VPN? My Norton VPN was pointing out of the USA. Set it to use United States and everything started working correctly!

I started having this same problem with Thunderbird (TB) not getting my mail from 

Comcast servers, starting sometime between 04/10/2025 and today, 04/12/2025.  I 

haven't changed ANYTHING on my PC.  The only difference is that I'm now at a B&B with 

Comcast and a Comcast modem/router

 combo (
a newer one, CGM4140COM, than I have at
home).  I come to this B&B twice a year and I've never had this problem.

I've spent the whole day now power-booting the PC, router,and looking at TB error
console msgs.  I have never had this problem before in all the years I've used
TB and Comcast (2 decades +)

I can get to my email fine via the web access.
I can send email via TB to the same account, so outgoing mail is OK.

I'm using all the Comcast preferred outgoing and incoming settings in TB that I've
had there for years (stated in previous posts above).
When I tell TB to get new messages, nothing happens, no popup for my password (I
don't use a PW manager in TB).  No msgs from TB and nothing appears in the TB
error console (Tools > Developer Tools > Error Console).

There has got to be some change at Comcast that they are not telling us about.

Also, I've had the "Third-Party Access" turned on at Comcast for at least 2 years
or so, so that's not the problem.

I'm not using a VPN or OpenPGP.

@gwws​ 

I found a fix on another page of this forum !

The problem appears to be that Comcast servers won't accep IPv6 traffic (this is 2025 guys !).  I don't know why this happens only when I try to get mail vs sending mail with TB, but the fix is to disable the opening of IPv6 connections from TB.  In TB, go to the config editor and change

the setting "network.dns.disableIPv6 " to TRUE.    It worked like magic for me.

Hope this helps others.

Thanks. I just ran into this problem this morning and this worked for me as well.

And now it's stopped working again, eventhough I set this to true.

@user_7q4frv Are you getting this error message when using our website?

@user_7q4frv​ 

same problem here.  says provider doesn't support OAuth 2.0.   I checked and my comcast email account is set up to allow access to 3rd party apps...

I recently asked about that and yes, Comcast now supports OAuth 2.0, so you might try changing that setting. 

Also, I just got a new laptop and I'm still doing set up and one thing I just did was setting up my comcast.net account in TB.  I let it do its thing automagically and I went back and checked the settings and OAuth 2.0 was set up.  I did a test email and could both send and receive with no problem.

Well if it makes you feel any better, you are not alone, this literally started for me this morning when I woke up, spent all day trying to find a solution with no luck. Tried all of the suggestions listed, I just keep getting that same error message on both IMAP and POP3.

Hello billw6560 thank you so much for taking the time and adding your voice to the conversation! Have we ensured Turn your access to third-party email programs on or off in Xfinity Email has been enabled? 

Yes, I tried the steps. Still not able to connect. Android email for Comcast is now working, but NOT on Thunderbird.

Hi @Spawne32, I'm I'm sorry to hear you're having issues receiving those errors when logging in. Have you tried the steps mentioned by @gwws? 

@billw6560​ 

Try changing your SMTP Authentication Method to OAUTH2.

Actually, change both incoming and outgoing to OAUTH2.

When I set this to Oauth2, I got the following pop-up message after a Login request:

Access Denied

You don't have permission to access "http://login.xfinity.com/login" on this server.

Reference #18.cc5dda17.1748380760.4207b2aa

https://errors.edgesuite.net/18.cc5dda17.1748380760.4207b2aa

Again, I'm logged into the web interface and can read/write emails, so my Login is good.

@billw6560​ The email server has my IP address blacklisted through Tmobile Home Internet. Figured it out last week. Try using a VPN to setup the email in thunderbird and it should work.

@billw6560​ can you update your TB; current is 139.0

And what is your connection to Edge Suite?

Another path you could take to solve this is going to the Microsoft help pages and the Thunderbird/Mozilla help pages.