Zoho is actually very good too but they (like Gmail) enforce IMAP connection limits, so it you have a lot of folders etc or use mobile clients like K9 that open a connection per folder then you can get errors very regularly.
The above is true for Zoho on the free plans anyway, but it may be different for the paid ones. But the free ones have pretty much all you could need if you don't run into the high number of IMAP connections issues.
If you have enough accounts to make it worthwhile I think Rackspace is supposed to be very good, but last I looked you needed a minimum of 5 accounts (I only had 4) so it didn't work out:
https://www.polarismail.com/
Zoho is actually very good too but they (like Gmail) enforce IMAP connection limits, so it you have a lot of folders etc or use mobile clients like K9 that open a connection per folder then you can get errors very regularly.
The above is true for Zoho on the free plans anyway, but it may be different for the paid ones. But the free ones have pretty much all you could need if you don't run into the high number of IMAP connections issues.
https://www.zoho.com/mail/
If you have enough accounts to make it worthwhile I think Rackspace is supposed to be very good, but last I looked you needed a minimum of 5 accounts (I only had 4) so it didn't work out:
https://www.rackspace.com/email-hosting/webmail