Error: "552 5.3.4 Message size exceeds fixed maximum message size" with Email Security.cloud

Products

• Email Security.cloud

Issue/Introduction

Despite raising your Message Size limit on the Email Security.cloud platform, you continue to receive bounce notifications or errors in Track and Trace referring to message size.

• 552 5.3.4 Message size exceeds fixed maximum message size
• 552 Message size exceeds fixed limit 
• 552 5.3.4 Error: message file too big

Cause

Many mail servers place a limit on the size of emails they will accept. For example, the default maximum message size for Microsoft Exchange is 10 MB. This value will prevent the delivery of larger emails regardless of the Maximum Email Size settings in the client portal.

Resolution

Adjust the settings on your MTA (Mail Transfer Agent) or Transport Hub.

Microsoft Exchange users, see the Microsoft article Message size limits in Exchange Server for assistance or contact your vendor.

For other MTAs, please refer to the support documentation provided by the vendor.

Also check "Maximum email size settings for Email Security.cloud" to be aware of difference in attachment size from actual email size.

How do I know an email was blocked by the Exchange Server and not the Email Security.cloud Maximum Email Size setting?

Emails rejected due to the Maximum Email Size setting will be clearly labeled "Email Size Limit" under the Service heading in the Track and Trace logs. In addition, in the Track and Trace detailed view there will be no Delivery section.

Emails that passed through our servers and reached the destination server will be populated with Deliver section along with the offending Recipient Server IP.

Additional Information

Are there alternative options so I don't need to modify my server settings?

Yes. At its core, Email was originally designed for text and not transport of large files. Online storage lockers emerged to fill this requirement. Some notable services include, but are not limited to, Box, Dropbox, Google Drive and Microsoft OneDrive. Utilizing these storage solutions will allow the sharing of larger files without the need to modify size limit settings or place an extra workload the mail server.

Related Articles

https://docs.microsoft.com/en-us/exchange/mail-flow/message-size-limits

https://docs.microsoft.com/en-us/exchange/recipients/user-mailboxes/mailbox-message-size-limits