Dear Zoho Support Team,

I have attempted to send multiple documents in several different ZIP files containing PDF and Word documents.

Initially, I received the following notification:

“When Office 365 tried to send your message, the receiving email server outside Office 365 reported an error.”

I then attempted to identify the file causing the issue by removing files one by one. However, I am now receiving the following error message instead:

“Unable to send message; Reason: 554 5.1.8”

At this point, I am unable to send any further emails.

I would highly appreciate urgent assistance in resolving this issue, as it is currently preventing me from conducting important business communication.