Outgoing iCloud server stopped working in Mail

3 days ago I couldn't send emails from my iCloud account. I noticed it from my iPhone (iOS 12.1.1) at first. I then attempted to send the mail from my iMac (Mojave) and it failed also. Yesterday I was successful in sending emails from my iCloud account from my MBP (High Sierra) and from my iPhone. However I still cannot send from my iMac and now from my iPad (iOS 12.1.1). The error on the iPad says the connection to the outgoing server p50-smtp.mail.me.com failed.

For the record I sent an email from my iMac from the iCloud account on 12/8/18, so it was working 9 days ago. I've not had any major changes to the system during that time. the only updates have been to Compressor, Medinfo, FullContact, OneDrive, OneNote, and Spark via the App Store. Only OneDrive and FullContact have been used. I believe I updated Cocktail during this time. As far as I can remember those are the only updates.

On the iMac I've logged out of my iCloud account and re-logged in twice. I tried to manually enter the SMTP settings for iCloud multiple times. I've searched for a solution but it's either very generic for and email server, specific to MacOS Server from a few years ago, or the problem resolved itself due to iCloud services being down. None of which apply in this case.

Short of doing a reinstall of the OS on the iMac and wiping and restoring the iPad, I'm at a loss as to what to do to fix it. For S&Gs I did a virus scan with AVG and it found nothing. I also had Cocktail run all Daily, Weekly, and Monthly scripts, clear all caches, etc.