Changed Zoho IMAP Access for Custom Domain

Zoho, a suite of business applications allowing, among others, having an email account using your own domain name, silently changed their access procedure, leading to Login failed messages in e.g. Thunderbird.

The gist of it is that you need to use imappro.zoho.eu for your IMAP server and smtppro.zoho.eu for outgoing SMTP server to continue using your own domain name.

The updated guide is at the Help pages for Zoho mail.

9. Incoming server hostname:
   If you are an organization user with a domain-based account, provide imappro.zoho.eu, select 993 for Port from the drop-down, and Normal Password for authentication.

10. For Outgoing server hostname:
    If you are an organization user with a domain-based account, provide smtppro.zoho.eu, select 465 for Port from the drop-down, and Normal Password for authentication.