Postfix Email Size Counting?

[Robin]

Hello

According to my knowledge postfix counts email size with an attachment sent to multiple receivers as one big email. For an instance: A user sends mail with 10 MB attachment to 3 receivers. Postfix assumes it is 3 x 10 MB = 30 MB mail. And when message_size_limit us by default 20 MB it rejects it.

Is there any way to order postfix to count the attachment of only once? I would like to keep off setting bigger message_size_limit.