How do I increase the maximum allowed attachment size in Webmail?

Question

How do I increase the maximum allowed attachment size in Webmail?

Answer

1. Log in to WHM as the root user.
2. Navigate to Home / Server Configuration / Tweak Settings.
3. Click the PHP tab.
4. Select the cPanel PHP max POST size (Minimum: 55; Maximum: 2,047) textbox.
5. Enter the desired value in the textbox.
6. Select the cPanel PHP max upload size (Minimum: 50; Maximum: 2,047) textbox.
7. Enter the desired value in the textbox.
8. Click the Save button.
9. Navigate to Home / Service Configuration / Exim Configuration Manager.
10. Click the Advanced Editor tab.
11. Scroll down to the Add additional configuration setting button.
12. Click the Add additional configuration setting button to add a new empty configuration option.
13. Select message_size_limit from the dropdown menu of the new configuration option.
14. Enter the desired value in the textbox. 
15. Scroll to the bottom of the Advanced Editor tab.
16. Click the Save button.

Note: Email attachments are encoded using base64 encoding. Base64 encoding typically results in a file attachment that is about 30 percent larger than the original file.

Additional Resources

Tweak Settings: PHP

Exim Configuration Manager: Advanced Editor