SMTP blocked with Monterey

pglatz wrote:

I recently updated my iMac to MacOS 12.3.1 from 12.3.0 - I can't remember when but it was probably at least a week ago. For the last few days, I have not been able to send email, using smtp.comcast.net at port 465, SSL. These are the settings I've used for the last few years, but suddenly stopped working. This is also happening on my MacBook, running the same OS. But I can use these settings just fine on my iPhone and iPad, and also on another iMac that's running Big Sur 11.6, which makes me think this is related to Monterey. Identical setting on all machines and devices.

While researching this, I came across this port checker at http://port-test-authsmtp.com - it reports port 465 is "blocked by browser," and says "The port is blocked by your browser for security - you may still be able to use it.". This may be a red herring, since I don't see anything in Safari settings, and quitting Safari isn't helping. I am not running a firewall, nor changed any other settings.

Send from with in Mail(?) or a share feature(?)

Is that the default...port 465, SSL ?

Have you contacted your Comcast.net support website, search: Support/Help/FAQ/known issues/compatibility/updates

Use the Connection Doctor...Show Details

Use Connection Doctor in Mail on Mac - Apple Support

can receive but not send email in Monterey issue, turn off note sharing feature:

Share notes and folders on Mac - Apple Support

ref:

Why am I able to receive emails but unabl… - Apple Community

Other possibilites— is Safari set as your default browser...