Outgoing server error - Excessive failed authentication ESMTP server temp. not available

@XfinityRyanE Thank you for getting back to me.  I checked the Thunderbird settings and they match the Outgoing Server ones shown in the article.

Thank you for checking on that for us, your time and efforts are truly appreicated. By chance have your tried removing your Xfinity email account from Thunderbird, and then re-adding it? If not, please try removing the account and setting it up following the instructions in the link provided. 

I deleted my email account from Thunderbird. Closed down Thunderbird and relaunched Thunderbird.  Then I added the email account according to the instructions. I then tried to send a test message and got the same error.

Sending of the message failed.
An error occurred while sending mail: Outgoing server (SMTP) error. The server responded:  resomta-ch2-14v.sys.comcast.net resomta-ch2-14v.sys.comcast.net Excessive failed authentication, ESMTP server temporarily not available, please contact support.

Thank you for trying those steps @user_ca1552. I am sorry to hear that didn't work as we had hoped. Let's get a little more specific. We know the Comcast email works and you can use it through the Xfinity website to send and receive email. What type of device do you use the third-party mail client on (phone, computer, laptop)? Have you attempted to reach out to Thunderbird for support yet? Just doing some quick investigating and it appears Thunderbird requires Java to be enabled. Do you have Java enabled on your device? I am sure working together we will get to the bottom of this.   

I am using a computer with Windows 10 Home installed.  This is the only device I use to read email.  I don't think I have Java installed but if that were the case why does it work sometimes and not work other times?  I haven't reached out to Thunderbird since so many folks have had this experience in the past and Thunderbird always sent them back to Comcast.

As mentioned by Bruce below, I don't sync my email (sync is turned off on the PC and phone) ....that I know of.  I only use the computer to do email.   How would I find the offending program, app or device?

My cell phone and tablet are turned off and the problem still exists.  Any advice on how to find the offending program, app or device?

Thanks! Please keep us posted. 

It has been a couple of days since I fixed the login issue on my tablet.  So far I haven't seen the failure message but I haven't been real active with email either.  I will continue to monitor and post another update next week.  Ann

We really appreciate that update and your time in reaching back out! We are here 24/7 if you do run into any additional issues! We look forward to your update next week! 

So it seems that fixing the login on my tablet has cleared this issue.  I also turned off 'sync' on the tablet as I don't need to read my email on that device anymore.  Thanks to Bruce for his comment/explanation as I wasn't even aware the tablet was trying to sign in.  So my approach was powering off all of the other devices and waiting at least a day to try to send emails, since right after powering the tablet and phone off the issue still occurred.  Then powering one on and checking to see if it was trying to access my email.  If you have several devices this could take a while but I am just happy the issue is resolved, in my case anyway.  Maybe this will help someone else who is experiencing the same failure message.

@user_ca1552. Great to hear! I appreciate your time working on it.

@PeterSpier

My issue returned just the other day too.  Over the holidays I started reading my email on my phone since I was away.  It took about a month since I logged in on my phone for the server to start complaining again.  It really isn't Thunderbird...it is your mail provider.  As soon as I had the issue I checked all of my devices again and then discovered my email was still logged in and running on my phone.  I closed the email app on the phone and waited a couple of hours before trying to send email from the PC again.  The Outgoing Server issue cleared and I haven't experienced any issues since.  I hope this helps you. Ann

I'm only using the one device.

I just received a callback fro the security team. The mail is now working again, though it isn't clear why. Either something has been reset at comcast or the router and modem reboot I did this morning fixed the issue, so we've closed my trouble ticket.

Well...the saga continues.  Today around Noon I started getting the failure message again.  I checked my phone and the email app is still disabled.  I turned my phone off and I still have the same problem.  Maybe I'll try resetting my router and modem.  If that doesn't work here goes another call into Comcast.  I wonder if I can get to the security team directly? It sure is an aggravating situation. Ann

I'm sorry this issue is still occurring for you, @user_ca1552 ! Did a reset of the modem and router help?