Pfsense squid reverse proxy emails with attachments are not sent via mac os, how to fix?

Question

Squid

Good afternoon, help please.
Is ms exchange, squid reverse proxy is configured.
Everything is OK, but if you connect mac os from an external network through Outlook or a native client, the letters go, but if you put an attachment in the sent letter, the letters hang in the outgoing ones and the client writes: the server is not responding.
Letters without attachments go fine on a poppy.
At the same time on Windows, on iPhones everything is ok.

They turn off reverse proxy and letters with attachments on a poppy go fine.

Can anyone come across?