Unable to send or receive Comcast email as of yesterday (using Thunderbird)
I've been using Thunderbird to access my Comcast email for two years now, without problems. Except yesterday & today, when I've been unable to send or receive emails, for no apparent reason. Yet, when I connect to my Comcast/Xfinity email via the Comcast browser website, sending and receiving of email works fine. This access problem began yesterday, 10/14/2025.
Same email address I've been using for about 20 years now, and same password. I made no changes to my Thunderbird or Comcast settings. Sending a test email to myself via the Comcast email website works fine. Clicking on the "Get Messages" icon in Thunderbird results in no action whatsoever. Sending a test message to myself in Thunderbird results in about a 40 second delay (usually it's 10 seconds), and then the error message "Login to server smtp.comcast.net with username don-peters@comcast.net failed." It then asks if I want to try again, but if I agree, the same error results. But there is also the option of "Enter new password". Click on that and the same error results, without even asking for a new password. But my password is OK, as evidenced by my Thunderbird settings and being able to log into Comcast browser email.
Yes, I've spent hours on the phone with Comcast on this issue, but they were of no help. One agent claimed that the issue was with Thunderbird, not Comcast, as its webmail worked fine. Two years ago, I had a similar problem I spent hours trying to solve. It turned out the problem then was due to Microsoft Outlook on my PC regularly trying to log into Comcast to ALSO download my email - BUT using the wrong password. Comcast interpreted these multiple failed login attempts as scammer attempts, and blocked ALL email logins from my PC. I fixed the problem by shutting down Outlook. But when I just spoke to Comcast they said the current problem was NOT due to my account getting blocked by them. But they couldn't give a reason for the blockage.
So, I now believe the problem lies with BOTH Thunderbird and Comcast. First of all, Comcast is somehow blocking my Thunderbird access attempts. But Thunderbird is also at fault for not reporting a SPECIFIC email login problem, so that we can address it - and fix it. If Thunderbird can be more specific as to why login attempts are failing, I can get back to them with the evidence - and hopefully solve the problem.
I've been using Thunderbird for about 30 years now, and I hate to give it up. But if this continues, I'll be forced to abandon Thunderbird.
Chosen solution
I think I found the problem, and surprisingly, it was on my end! It seems to have been due to my USB-C port expander! Whodathunk!
When this problem started, I also encountered intermittent problems connecting to my mouse and keyboard. At first I assumed my tablet PC was causing the problem(s). But then I noticed that my PC sometimes wasn't detecting some thumb drives connected to my USB expander port. Lots of tests I did showed that my PC was fine, but that the problem was with my multiport USB expander. Consequently, I ordered a replacement port expander and did the replacement yesterday. That fixed the intermittent port connection issue. But to my amazement, it also cleared up the Thunderbird to Comcast connection issue! Why the two were related is beyond me, since even when the expansion port seemed to be working, I still had these email problems. In fact, after the replacement, I spent a day or two constantly testing my email to make sure the problem went away. It did, and all is fine now.
Apparently, the expansion port, even when it was "working", was still somehow corrupting the Thunderbird to Comcast connection link.
Live and learn! Don
Read this answer in context 👍 0All Replies (4)
Hmmm, I just checked my Thunderebird version - it's 140.4.0. It's the latest version, AND was automatically installed yesterday, which is exactly when this login problem started happening. So, was this a super coincidence, or was the update the cause of the problem????
Don Peters said
or was the update the cause of the problem????
Probably not. It is far more likely you have what amounts to fairly standard post update problems with your antivirus product of choice. Only Defender, that I know of, is exempt and it does not scan email.
This is an exceeding common issues with the leading antivirus brands from Gen Digital
Check the firewall component. Go to addons and themes on Thunderbird menu and search for import. Does it return a load of results (I get 40) of some cryptic error message.
Chosen Solution
I think I found the problem, and surprisingly, it was on my end! It seems to have been due to my USB-C port expander! Whodathunk!
When this problem started, I also encountered intermittent problems connecting to my mouse and keyboard. At first I assumed my tablet PC was causing the problem(s). But then I noticed that my PC sometimes wasn't detecting some thumb drives connected to my USB expander port. Lots of tests I did showed that my PC was fine, but that the problem was with my multiport USB expander. Consequently, I ordered a replacement port expander and did the replacement yesterday. That fixed the intermittent port connection issue. But to my amazement, it also cleared up the Thunderbird to Comcast connection issue! Why the two were related is beyond me, since even when the expansion port seemed to be working, I still had these email problems. In fact, after the replacement, I spent a day or two constantly testing my email to make sure the problem went away. It did, and all is fine now.
Apparently, the expansion port, even when it was "working", was still somehow corrupting the Thunderbird to Comcast connection link.
Live and learn! Don
Good snowy morning, all! I have this issue, too, now for the second time. The first time was 11//10/2025 for roughly a 1 to 2 weeks. Spoke with comcast/ xfinity on 11/13/2025. Started mysteriously working again several days later, some time the following week. Then last Thurs., started again through this morning. Have tried all of the xfinity things. They says it's Mozilla/ Thunderbird. Our Thunderbird is updated fully. I do not have any usb expander equipment, no new equipment. Getting no antivirus popups, so no idea there, not sure what would be new to make happen, get fixed, then happen again. Please help as soon as possible.
Modified by RimersburgBoro
You must log in to your account to reply to posts. Please start a new question, if you do not have an account yet.