by lunarg on April 14th 2010, at 20:22

Like any other MTA, Postfix has a maximum message size that it allows to pass through. By default, when not defined, it is set to 10 MB.
To change it, add/change the following in

message_size_limit = 15728640

This sets the limit to 15 MB. To make it unlimited, set it to 0.