Good evening support team,

We have an email recipient that we get an email delivery failure on.

The bounce reason given in the report is:

"Please turn on SMTP Authentication in your mail client. sender11-op-o11.zoho.eu [31.186.226.225]:17058 is not permitted to relay through this server without authentication."

SMTP Authentication is turned on within Outlook for IMAP access and we are able to send emails perfectly fine to everyone else.

Do you have any suggestions?

Many thanks