I just started having trouble with Spectrum mail (sending and receiving) about a week ago on my Mac, iPhone, and iPad using Apple Mail. It seems Spectrum/Charter updated server names and finally made it mandatory for all users. Spectrum customer support was completely unhelpful aside from sending me emails and directing me to webpages with server settings that were incomplete. Finally, I got it to work on all my devices. The key seemed to be to delete the Spectrum email account from my Apple mail on each device. Then, to set it up from scratch one by one. When I just tried to do an update to incoming server host name, I was able to update. When I tried to update the outgoing server host name, it just kept trying to verify - but never succeeded. Deleting the Spectrum mail account and starting over worked for me.

Email Settings

Username: Your full Spectrum email address

Password: Your Spectrum email password

SSL: On

Protocol: IMAP

Incoming Email Server: mobile.charter.net

Port: 993

Outgoing Email Server: mobile.charter.net

Enter your User Name and Password even though it may say optional when in Outgoing Email Server settings

Set Authentication to Password