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SMTP error: Message size exceeds server limit Roundcube | How to fix

by | Nov 5, 2021

“SMTP error message size exceeds server limit” in Roundcube giving you trouble?

As a part of our Server Management Service, we offer solutions to every query that comes our way.

Let’s take a look at how our proficient Support Team helped a customer recently resolve their SMTP error message in a jiffy.

What is SMTP error message: Size exceeds server limit?

Have you been having trouble with large email attachments that hits the upload limit even if the attachment has not exceeded the limit? You have come to the right place! Our Support Engineers are here to help you out.

Generally, emails are encrypted in Base64 before being sent out. This helps increase the size of the mail. However, this increase in size may trigger the ModSec upload limit rules.

This prevents the email from being sent even though it appears to be below the limit when initially sent. You can see the documentation related to this here.

How to resolve SMTP error message size exceeds server limit Roundcube

An effective way of resolving this error is to increase the message_size_limit in the Exim Configuration Manager. Try these steps by our Support Engineers recommend to get this done:

  1. First, navigate to Service Configuration.
  2. Then, go to Exim Configuration Manager.
  3. After that, head to Advanced Editor.
  4. Next, select CONFIG sections.
  5. Finally select message_size_limit.

In case message_size_limit is not listed, we can add it in the CONFIG section as a new configuration entry.

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To sum up, we learned the reason behind the SMTP error message size exceeding the server limit in Roundcube. Our Support Engineers also demonstrated to resolve this error in a jiffy.


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