Error: "Send test email message: The server responded: 550 5.7.1 Authentication." When Setting up POP3 and IMAP Account in Outlook – KerioConnect Support
email server - Changing hosts resulting in 554 5.7.1 <xxx@domain.tld>: Relay access denied - Server Fault
554 5.7.1 <zoho@yourdomain.com>: Relay access denied | Zoho Mail Error
FIX: Relay Access Denied 554 5.7.1 Error in Outlook (Solved) - wintips.org - Windows Tips & How-tos