How to use a different SMTP mail relay for sending emails with a message size over 10MB

Question

I use Amazon SES as a mail relay service for my emails as my server host blocks connections out on port 25. SES works great, however occasionally users send large attachments (>10MB). Whilst I could just every time suggest they upload their attachments somewhere and send a URL, this becomes tiresome and sometimes too complicated for my users. I have another mail relay available that allows me to send a smaller number of larger emails and so would like to send messages larger than 10MB through an alternate mail relay, and all other mail through Amazon SES still.

How would it be possible to achieve this in a postfix smtp server?

Answer 1

I don´t know an exact solution for you but it won´t works out of the box with postfix. You have to install a policy server which could check the mail size and dependent from the result it should resend the email to postfix on an own port there you could set up a different configuration with a special relay server.

There are a lot of policy servers for postfix - so please check yourself.