Reject oversized emails
Email Security accepts emails up to 50Mb inbound or outbound. Should your mail server (Domain Route) not accept this size of message, you can reject the message at the point of SMTP connection. This will make the connecting server create a Non-Delivery Report (NDR) for the sender.
If you configure a mail size rule in message rules the sender will not be advised that the email was not received by the recipient.
NDR's are not sent from your Mail Server (Domain Route) back to the Internet if your server rejects the message and Email Security routes it. This is due to security policies that help to avoid being blacklisted due to backscatter and NDR spam.
Disabling the Maximum Mail Size connection rule may result in email being accepted which later cannot be released. This is due to file size compression as discussed in RFC 2045 section 6.8: Content-Transfer-Encoding
To change the 50mb limit:
- visit your USS Dashboard and click Products ⟶ Email Security ⟶ Connection Rules.
- Double-click the Maximum Mail Size Rule to edit it.
The Rule might be called Large Files on your system.
- Find the Email Size Condition, and click
. - Choose a new limit from the Condition Value dropdown.