I am using OS 10.13.3 and have not made any changes to my settings. I verified the info in preferences and they are correct. The error message says my server can't authorize the action.
iMac, OS is High Sierra 10.13.3
see this link
I did that and all the items had green dots, all settings are correct and my iPad and iPhone send just fine with the settings.
is this your Apple ID ending with an Apple owned domain or some other hosting service?
Another service but it isn’t new...i’ve used it for years and it works on my other Apple products. It receives my mail it just won’t send.
check their Knowledge Base and see if they changed their configuration requirements. Or call them.
If it's just that email and others work it's very possible their outgoing server is messed up.
I don’t think they changed anything...I can send email from both my iPad and iPhone.
My iMac quit sending email
