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[Discuss] Thunderbird not connecting to Comcast IMAP server

This has apparently resolved itself, by connecting the system into a 
different port on the Internet gateway. For added measure, I plugged the 
other system into the first system's original port and TB continued to 
work on the other system as normal.

What changed in switching the port, other than the internal IP address? 
Haven't a clue...

On 10/9/19 5:27 PM, epp at wrote:
> This appears to be an IPv6 issue on this system, since TB otherwise 
> works fine on the other system.
> I used TB's Config Editor and toggled the entry for 
> network.dns.disableIPV6 from "false" to "true". Relaunched TB and it 
> worked. Toggled it back to "false" and TB again fails to connect to 
> Comcast.
> So the question now, is: What changed on /this/ system that is 
> apparently now preventing Thunderbird (and Evolution) from connecting 
> via IPv6 and how to correct it?
> There is another entry in the config that is supposed to flip the 
> protocol to IPv4 (, if there is no 
> response via IPv6 within a short amount of time and that entry is set 
> to "true".
> On 10/9/19 9:16 AM, epp at wrote:
>> Both Fedora 30, with the same packages.
>> -----Original Message-----
>> From: Derek Atkins <derek at>
>> To: epp at
>> Cc: discuss at
>> Sent: Wed, 09 Oct 2019 8:59 AM
>> Subject: Re: [Discuss] Thunderbird not connecting to Comcast IMAP server
>> Are both systems Fedora 30 with the same sets up upgrade packages?
>> -derek
>> On Wed, October 9, 2019 8:52 am, epp at wrote:
>>> Nothing changed on this end.
>>> It connected fine up until Sunday night. But I can't explain why TB
>>> successfully connects to Comcast on one system, but not on the other.
>>> -----Original Message-----
>>> From: Derek Atkins <derek at>
>>> To: epp at
>>> Cc: discuss at
>>> Sent: Wed, 09 Oct 2019 8:32 AM
>>> Subject: Re: [Discuss] Thunderbird not connecting to Comcast IMAP 
>>> server
>>> Did anything change on your end?? Did you take any updates?
>>> Could it be a TLS ciphersuite incompatibility issue?
>>> I believe that F30 disabled a BUNCH of old ciphers.
>>> If Comcast is running an older IMAP service you might not have 
>>> compatible
>>> ciphers anymore.
>>> -derek
>>> On Wed, October 9, 2019 8:27 am, epp at wrote:
>>>> Beginning this past Monday, Thunderbird and the SeaMonkey suite (on
>>>> Fedora
>>>> 30) mysteriously stopped connecting to Comcast's IMAP mail server.
>>>> In trying to diagnose the issue, I also installed Evolution, which 
>>>> also
>>>> failed to connect.
>>>> After removing the Comcast accounts from Thunderbird, attempts were 
>>>> made
>>>> to add them back in, however when Thunderbird attempted to check the
>>>> password, that process becomes stuck, as if Thunderbird cannot resolve
>>>> the
>>>> IP address(es) for the Comcast server. I let it sit like that for 15
>>>> minutes without success, then clicked Cancel.
>>>> Thunderbird otherwise connects to non-Comcast IMAP servers perfectly.
>>>> I also have Geary installed and that successfully connected to the
>>>> Comcast
>>>> server, yet the other three email clients could not.
>>>> Could this be an issue on Comcast's end? If it were a DNS or resolver
>>>> issue, then nothing would connect.
>>>> I have Thunderbird installed on a second system and it connected to
>>>> Comcast successfully on that, last night.
>>>> Thanks for any replies/suggestions.
>>>> _______________________________________________
>>>> Discuss mailing list
>>>> Discuss at
>>> -- 
>>> ??????? Derek Atkins???????????????? 617-623-3745
>>> ??????? derek at
>>> ??????? Computer and Internet Security Consultant