slow outgoing email

Friends--

For the last 2 months or so, outgoing email using comcast has been extremely slow.

About 2/3 of the emails I send, take 30 to 60 seconds to actually send. The other 1/3 go out almost instantly, like before. I remember having a similar problem maybe 5 years ago, and after I posted here, and someone from Comcast interacted with me, the problem was fixed. For years. Till now.

I am using Thunderbird 68.7.0 (64 bit) on 18.04 Ubuntu. Settings: smtp.comcast.net port 587, starttls.

(BTW, I tried searching the forums and found several likely threads for answers (latest was 2019), but I could find no way to actually read the threads. I clicked all sorts of things, and everything seemed to go to a page "What can we help you with?" Got any hints on how to use the search?)