The postfix MTA is configured by default with resource limits that safeguard the stability of the server. One such parameter is the maximum email size, which is configured to approximately 10 MB by default. If you need to send emails larger than 10 MB:
- Backup the /etc/postfix/main.cf configuration file
- Edit the /etc/postfix/main.cf configuration file
- Add a line to the bottom of the file with the desired new size. For example, if you wish to increase the size to approximately 25 MB:
message_size_limit = 25000000
- Save the file
- Reload sendmail
service postfix reload
For more information, please refer to the postfix documentation.