can't connect to AOL smtp server

Hello,

In the past week or two I have not been able to send email on my home iMac, from my AOL account. Mac Mail tries for a while, then reports that the SMTP connection to the server smtp.aol.com failed.

Connection doctor reports the same failure, specifically a timeout. The thing is, in the detail and logs, Mac Mail is using port 465 for smtp.aol.com, when AOL states on their help website that the proper port for their SMTP server is 567. As far as I can see Mac Mail never tries that port.

I tried to edit the SMTP server list, and set up a new AOL SMTP server (called AOLnew) with the correct port. I select the new entry and select OK, immediately the new SMTP server entry disappears. Mac Mail won't retain a new AOL SMTP server I create (perhaps because it is the same SMTP address as the existing AOL (offline) entry?).

So I'm stuck. The Mac mail automatics time out trying to connect to AOL SMTP, nor will Mac mail remember a new AOL SMTP server with the correct port.

I've tried re-installing macOS Sierra, and also tried deleting the Mail preferences file in my Library. I've also tried (temporarily) turning off both Little Snitch and the Apple firewall, in case they were blocking the connection. None of these adjustments have helped. My other email accounts are working fine on my iMac, and My AOL email works fine at work on a Mac mini using the same (latest) version of macOS Sierra.

Does anyone have any suggestions?

Thank you.