For POP Incoming Server: Mail.acsalaska.net
   Port: 995
   Security: SSL
   Authentication: Password
   Username: Full Email Address With domain (example: 907*******@acsalaska.net)
   Password: Email password
   Outgoing server: Mail.acsalaska.net Port: 465
   Security: SSL
   Authentication: Password
   Username: Full Email Address With domain (example: 907*******@acsalaska.net)
   Password: Email password
   For IMAP Incoming Server: Mail.acsalaska.net
   Port: 993
   Security: SSL
   Authentication: Password
   Username: Full Email Address With domain (example: 907*******@acsalaska.net)
   Password: Email password
   Outgoing Server: Mail.acsalaska.net Port: 587 or 465
   Security: SSL
   Authentication: Password
   Username: Full Email Address With domain (example: 907*******@acsalaska.net)
   Password: Email password
   Unencrypted Outgoing Server: Mail.acsalaska.net Port: 25
   Security: None
   Authentication: Password
   Username: Full Email Address With domain (example: 907*******@acsalaska.net)
   Password: Email password

I see two questions from you. this and one in 2016. https://support.mozilla.org/en-US/user/alaskawill/questions so I have no idea where you contacted Mozilla support as this site is it. I looked at the providers web site https://www.alaskacommunications.com/Support/Email and will copy what they say your connection settings should be. For POP Incoming Server: Mail.acsalaska.net Port: 995 Security: SSL Authentication: Password Username: Full Email Address With domain (example: 907*******@acsalaska.net) Password: Email password Outgoing server: Mail.acsalaska.net Port: 465 Security: SSL Authentication: Password Username: Full Email Address With domain (example: 907*******@acsalaska.net) Password: Email password For IMAP Incoming Server: Mail.acsalaska.net Port: 993 Security: SSL Authentication: Password Username: Full Email Address With domain (example: 907*******@acsalaska.net) Password: Email password Outgoing Server: Mail.acsalaska.net Port: 587 or 465 Security: SSL Authentication: Password Username: Full Email Address With domain (example: 907*******@acsalaska.net) Password: Email password Unencrypted Outgoing Server: Mail.acsalaska.net Port: 25 Security: None Authentication: Password Username: Full Email Address With domain (example: 907*******@acsalaska.net) Password: Email password I suggest you open your account settings and compare them to those you are using with those published by your mail provider. You were advised about antivirus programs being problem children back in 2016, nothing has changed with that. They are still the primary failure point in email connections. Generally I recommend disabling all mail scanning to test if that might be an issue, and even all scanning for a time to test that. Basically antivirus programs tend to use hacking to do their scanning and this extends to untrusted self signed certificates. So using unencrypted connection setting will reduce your security, but eliminate this certificate issue. You might try it an see if that helps.