I am getting an error 421 Excessive failed authentication.

[Leopreferred]

Hi, I am getting this message when I try to send emails. I can recieve them, but not send them. It looks like other people are having the same issue. The same thing happend last week and now again? Please help me figure this out.

An unknown error has occurred.

Subject 'Scan_20191103 (2).pdf'
Server Error: 421
Server Response: 421 resomta-po-15v.sys.comcast.net resomta-po-15v.sys.comcast.net Excessive failed authentication, ESMTP server temporarily not available
Server: 'smtp.comcast.net'
Windows Live Mail Error ID: 0x800CCC67
Protocol: SMTP
Port: 587
Secure(SSL): Yes

[BruceW]

If @ComcastAntiSpam or another employee doesn't respond here in the Forums, Comcast Security Assurance should be able to help. You can reach them at 1-888-565-4329 (from https://internetsecurity.xfinity.com/help/report-abuse/). Note that this is NOT one of the general customer service numbers. The first-line reps there are sometimes not very helpful, so you may need to be persistent and keep at them until you get a satisfactory answer.