If you're going to post here, please stop with the UPPERCASE. The issue of a blacklisted IP address is not specific to an email client. If you post the complete message, some advice may be forthcoming. I presume you are getting the message when sending email.

I don't mind the all-caps, as a lot of people don't realize that's the keyboard equivalent of yelling. My dad used to type in all-caps too.

Regarding the Thunderbird "temporarily blacklisted IP address" message about my Comcast email account, I have the same problem, and have tried troubleshooting mode with only temporary improvement, as well as uninstall-reinstall without benefit. I just now contacted Comcast, and they are having a level 2 tech support person look into it. For me, the problem is occurring only on 1 of 2 laptops (fortunately). Possibly coincidentally, about 2 weeks ago, I upgraded this laptop from W10 to W11, but the error message began only yesterday. So, I don't have any solutions yet, but will try to provide updates when I do hear from Comcast.

If anyone has additional helpful suggests, I'm open to hear from them.

Velma

Thank you Velma. Glad to hear that other's are having similar problems. Sorry for the Caps but I did not realize it at the time and did not mean to OFFEND others.

My issue began at the end of March and has been a long month of talking to Comcast to no avail. They claim all is well on their end and "it must be Thunderbird....talk to them".

I get the following error messages when Thunderbird tries to pull E-mails from two Comcast accounts: 1. Login to account (E-mail account.comcast.net) failed. 2. Login to server imap comcast.net with usernames failed. 3. Alert from account (E-mail account) temporarily blacklisted ip address - Try again later.

If i restart my personal desktop computer Thunderbird pulls the E-mails from Comcast and then after five or ten minutes the above error messages appear.

I moved to Outlook and get error messages that my Comcast needs to be updated. No E-mails and then later they start coming in little groups along with the error messages.

It seems to be a circular chase....not me, but them, not them but you.

Thank you for your reply.....noting that others are having the same issue.

We commonly see problems with comcast, but without people sharing details, we cannot assist.

An update to the blacklisted ip address and not connecting to a server.

I spent some four hours on the phone with Comcast support on 4 May. Worked my way up from the initial support level, to tech support, and to the next higher level of tech support. Went through the same process at each level, answered the same questions, and comcast went through their checks, even wanting a new password for the main account. The tech was referencing documents you can find on line regarding Thunderbird and Comcast issues. At the last tech level the support person ran out of options and opted as a last effort to just "reboot/restart" the modem line from their end. With the modem reboot taking place I opted to do other things. Approximately five hours later I decided to "look again" at Thunderbird. I re-entered the new password under the Thunderbird program to set-up an existing account. Bingo. it worked, Thunderbird pulled the E-mails and has been working just as it did before.

Even Outlook is working and getting all the E-mails with no problems.

So far no error messages or ip blacklist messages.

The blacklisted ip error message was not Thunderbird.

Servers use spam filters to check mail before they send emails and the receiving servers do the same. Your computer ip address had got onto a server spam filter list and that was why you kept getting the error message from the relevant server.

Usually, the error message advises you to check a specific spam filter and one of the most common websites to check is this:

• https://check.spamhaus.org/

The ip address range is controlled/issued by your internet service provider.

If you are using Windows OS then the info at the link below would help you to find out your current ip address:

• https://support.microsoft.com/en-us/windows/find-your-ip-address-in-windows-f21a9bbc-c582-55cd-35e0-73431160a1b9

I would have advise you to try to force a new ip address for your computer. One method you could try would be to exit all programs, switch off computer and then perform a reset on the router. Usually there is a 'reset' button on the side of the router which you can use. Sometimes completely disconnecting the router can work as well - wait about 12 seconds and then switch it on. Once it is all up and running, boot up computer and open Thunderbird.

However as you mention 'comcast' then it's possible you are using xfinity as isp.

I have located some information at the following link which may be of interest should this issue present itself again.

• https://www.xfinity.com/support/articles/releasing-and-renewing-ip-address