Let us take a closer look at how to configure the postfix message_size_limit. With the support of our Server Management service at Bobcares, we can give you a step-by-step guide on the process.

Postfix message

It is a well-known Mail Transfer Agent (MTA) that can establish routes and transfer emails. This cross-platform server is open-source, free, and available for installation on most UNIX-like operating systems.

 postfix message_size_limit

The default message size limit for POstfix is 10240000). A message’s maximum size in bytes, including envelope information. The value cannot be more than LONG MAX (typically, a 32-bit or 64-bit signed integer).  When a bounce message size exceeds the local or remote MTA’s message size limit, overly tiny values will result in the loss of non-delivery notices. A fresh Postfix installation’s maximum attachment size is set to 10 MB by default (10240000 bytes). That’s definitely too tiny for most current applications.

The default size restriction is in /etc/postfix/main.cf. On a fresh or default installation, the configuration variable postfix message_size_limit may not be present. Use postconf with -p: to view the option even if it isn’t in the configuration file. 

postconf -p | grep message_size_limit message_size_limit = 10240000

Use the following commands to modify it to 30 MB:

sudo postconf -e 'message_size_limit = 30720000'
sudo postfix reload

It is even feasible to go higher. Google had a 25 MB limit as of approximately 2021, while Office 365 had an adjustable 1 to 150 MB limit.To test if the postfix message_size_limit changes were effective, run postconf again: postconf | grep message_size_limit
message_size_limit = 30720000

Making the change via Webmin

To change the message size limit through Webmin firstly, go to servers from Webmin and click on the mail server from the drop-down options. Go to general resource control and a page on the same will open up. The window displays All of the default configurations on the postfix message_size_limit and other details. Go to the ‘Max size of a message option’ in the window and click on it to change the values. click on the Save and Apply button after the necessary configurations to integrate the changes into postfix.  

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Conclusion

To conclude,  postfix message_size_limit can be reconfigured either by giving specific commands to postfix or directly from the Webmin within a few simple steps.