Use mail.b.hostedemail.com as incoming and outgoing server.
Tried that with one of the recalcitrant accounts on my iPhone and it does not help.
The main problem account that i had the really urgent problem with just came good overnight with incoming mail server <mail.companydomain.com.au>
This is very perplexing and annoying.
One of the accounts on one of our macs running mac mail continues to drift in and out of working and not working. This is a real problem to us as about to travel and must have working without flaws.
Again <mail.companydomain.com.au> works with all other domains we work with with other companies.
Your help is appreciated.
Send me a private message with the problematic accounts and I will take a look.