Charter Spectrum mail not working on Mac since Mojave update.

Charter website says use mobile.charter.net for outgoing and incoming servers. Works on iPhone and iPad but not on Mac. Apple mail support page says use mail.charter.net for incoming and outgoing. mail.charter.net works until i close my MacBook air and come back to it later...then it's offline and can not verify or timed out. Rebooting doesn't work. Deleting mailbox and adding it back works only sometimes. Charter support was of no help. Any ideas? The ports are correct as per website. Passwords are used as authentication. Thanks