Email Not Working - ESMTP server temporarily not available

I live in a retirement complex with a couple of hundred other residents. Many of the other residents use Xfinity for email.  About 5-6 weeks ago, a number of us began having sporadic email problems when trying to sync our Xfinity email using a local mail client -e.g., Apple Mail, Outlook, Thunderbird, etc. 

I've enlisted the help of a technical person to diagnose, and what we found by turned on Outlook's "transport logging" is that the Xfinity mail server is failing authentication with the error, "Excessive failed authentication, ESMTP server temporarily not available."  What's strange is that the email client will work fine for a while, then suddenly stop working, and then it will mysteriously start working again a bit later. No configuration changes  are made (i.e., the username and password are NOT changed) between when the email works and stops working. I only have two devices (laptop and desktop), so his rules out the issue seen on other posts where users have multiple devices, and one device has the wrong password.  What's even stranger is that one of my devices will work (email client connects and syncs email) at the same time my other device errors out with this problem!!!

Here's an excerpt from the log (email address obscured) where it wasn't working, and then less than a minute later it was working:

2022.11.02 13:21:38 SMTP (smtp.comcast.net): Begin execution
2022.11.02 13:21:38 SMTP (smtp.comcast.net): Port: 465, Secure: SSL, SPA: no
2022.11.02 13:21:38 SMTP (smtp.comcast.net): Finding host
2022.11.02 13:21:38 SMTP (smtp.comcast.net): Connecting to host
2022.11.02 13:21:38 SMTP (smtp.comcast.net): Securing connection
2022.11.02 13:21:39 SMTP (smtp.comcast.net): Connected to host

2022.11.02 13:21:39 SMTP (smtp.comcast.net): <rx> 421 resomta-c1p-023412.sys.comcast.net resomta-c1p-023412.sys.comcast.net Excessive failed authentication, ESMTP server temporarily not available
2022.11.02 13:21:39 SMTP (smtp.comcast.net): End execution
2022.11.02 13:21:39 [Edited: "Personal Information"]: ReportStatus: RSF_COMPLETED, hr = 0x800ccc67
2022.11.02 13:21:39 [Edited: "Personal Information"]: Synch operation completed
2022.11.02 13:22:08 [Edited: "Personal Information"]: Synch operation started (flags = 00000001)
2022.11.02 13:22:08 [Edited: "Personal Information"]: UploadItems: 1 messages to send
2022.11.02 13:23:24 SMTP (smtp.comcast.net): Begin execution
2022.11.02 13:23:24 SMTP (smtp.comcast.net): Port: 465, Secure: SSL, SPA: no
2022.11.02 13:23:24 SMTP (smtp.comcast.net): Finding host
2022.11.02 13:23:24 SMTP (smtp.comcast.net): Connecting to host
2022.11.02 13:23:24 SMTP (smtp.comcast.net): Securing connection
2022.11.02 13:23:24 SMTP (smtp.comcast.net): Connected to host
2022.11.02 13:23:25 SMTP (smtp.comcast.net): <rx> 220 resomta-a1p-076786.sys.comcast.net resomta-a1p-076786.sys.comcast.net ESMTP server ready

While scouring Xfinity's support site, we came across the following information on Xfinity ⋅ Service Policy Assurance, where it states:

9. Watch the sending limits

        Comcast allows 25 simultaneous connections per sending IP address.
        Comcast allows 100 recipients per message.
        Comcast allows a throttle rate based on your sender reputation and authentication.

 

Internet is provided to the residents living in Westley at Tehaleh (the retirement complex where I live). As a result, anyone using connecting to Xfinity email would appear to have the same public IP address (65.141.209.42). 

We currently have a hypothesis that there is something on Xfinity’s side that blocks the email connections if there are too many people trying to connect to email at the same time. This would explain why this started occurring a 5-6 weeks ago when a number of new residents moved in, and also why the problem is intermittent.

Is there someone at Xfinity who can PLEASE help us investigate this issue given that it is affecting multiple people who live in my retirement community, and rely heavily on our email working?