Mac Mail - unable to establish accounts
I have 2 MBPs (13" & 17") both running High Sierra 13.6. and Mail v11.5 (3445.9.5) and have had a LOT of problems in the last 9 months trying to establish Mail accounts for Earthlink & Gmail on them. I had no problems when they were both POP accounts, but read that IMAP accounts work better when managing mail over several devices. I have inquired on these forums in the past without any resolution.
I have been successful in converting all my POP accounts on both mail servers for my MBP 17", my iPadPro, my iPhone 7, and my Mac Mini running Catalina. They all work(ed) great. But I could NEVER establish an IMAP account for Earthlink on my 13" MBP! Then as time went on, each of the other IMAP accounts on both the MBPs have gone offline with no resolution for at least a month! I have to read/work my mail from the 2 respective servers on line and in both cases the UID/PW works in those instances.
Connection Doctor repeatedly fails to establish a connection any more on either account for either incoming (IMAP) or outgoing SMTP servers. from these 2 MBPs. Then I thought to switch to using Mozilla's Thunderbird on both and it worked fine for a week on the 13" and then started doing the same thing, and I could NEVER get one established on the 17"!
When I have the IMAP acct established on the MBPs they just won't go online and connect with the respective servers. In the cases where I don't have an IMAP account established (Thunderbird) it's because they won't establish!
I was thinking I had a problem with 'Mail' and I din't know how to reload a fresh copy. but when I tried Thunderbird instead, I experienced the same problem! Now I can only presume I have some sort of Mail (or Thunderbird) related problem with High Sierra!
Do these symptoms ring a bell for anyone? I think I am out of options.
Brian
MacBook Pro 17", OS X 10.11