At Theory7 you can send email attachments of up to 100MB by default. That's generous, especially compared to other providers, where a limit of 25MB is common. But what if you want to raise or lower that limit? In this article we explain exactly how to do that with Exim, including examples for DirectAdmin, Plesk and cPanel.

Important: this is only possible on a Theory7 VPS or Dedicated Server. Do you use shared hosting? Then you can't change these settings.

The default limit at Theory7: 100MB

As a Theory7 customer you can include attachments of up to 100MB per email message. That is our default setting. Want to change it? Then read on.

Changing the email attachment limit in Exim

Exim is the mail server used on our VPSs and Dedicated Servers. You can change the limit with the configuration parameter message_size_limit.

Step 1: Open the Exim configuration

Open the file /etc/exim.conf over SSH with your favorite editor, for example:

sudo nano /etc/exim.conf

Step 2: Find or add the setting

Look for the line message_size_limit. If it isn't there, you can add it yourself. For example:

message_size_limit = 150M

This allows Exim to accept attachments of up to 150MB.

Step 3: Restart Exim

Don't forget to restart Exim to apply the changes:

sudo systemctl restart exim

Setting it in DirectAdmin, cPanel or Plesk

DirectAdmin:

  1. Log in to your DirectAdmin panel.

  2. Go to Admin Settings > Exim Configuration Manager.

  3. Search for message_size_limit.

  4. Change the number of MB and save.

cPanel (WHM):

  1. Log in to WHM.

  2. Go to Exim Configuration Manager > Advanced Editor.

  3. Add or change:
    message_size_limit = 150M

  4. Click Save.

Plesk:

Plesk has no GUI for Exim configs. So you have to follow the SSH steps above for /etc/exim.conf.

Why large attachments are sometimes a bad idea

Even though you can technically send 100MB (or more), that doesn't mean every email provider will accept it. Many receiving providers such as Gmail, Outlook or Yahoo block emails with attachments that large.

Alternative? Use cloud storage:

Simply include a download link instead of an attachment.

FAQ

Can I also change the limit on shared hosting?
No, this only works on a Theory7 VPS or Dedicated Server.

What happens if I send an attachment that is too large?
The email is rejected or never arrives at all. You often get a "message too large" error.

What is a safe limit to set?
Stay around 25 to 50MB if you want to be sure the email arrives everywhere. For internal use you can go higher.

Ready to set up your email perfectly?

Get started now with creating an email address at Theory7

Need help? Feel free to get in touch via our contact page