You receive a Non-Delivery Recipient (NDR) for a mail rejected by HES. The details show the following reason:
Malformed Email Rejected
The issue occurs because the mail format is incorrect and cannot be processed by its scanner. This usually happens to emails with attachments.
To resolve the issue, do any of the following:
Option A. For file attachments of Microsoft Office 2007 or later versions
Refer to the following KB article: Some valid Microsoft Office 2007/2010 files are being bounced or rejected by Hosted Email Security (HES).
If the mail is still rejected, refer to the following KB article: Mails with attached compressed files are being bounced by Hosted Email Security (HES).
Option B. For all other types of file attachments
Contact Technical Support and provide them an original copy of the rejected mail from the sender.
You may also ask the sender to password-protect the attachment if you need the email right away. This will let HES bypass the scanning of the attachment and the mail will be delivered to your user as long as it did not trigger the other rules and did not violate any of the Global Limits.