Hello,

Some customers reported that when a mail sent from Mac mail having attachment is received by Mac mail, the mail formatting is lost.

I connected a Mac mail to a test account via SMTP/IMAP and sent a mail to itself.

The received mail looks like this:

When it should be like this:

If I do the same test with another mail server (not SM), all is good.

It looks to me here that SM is altering the mail content at some point... I would say it's at the receiving time as if I send the mail from an external service to the same mailbox on SM connected to Mac OS, the mail formatting is also dropped.

EDIT: From memory this is a problem that was historically present in some older builds and was fixed (at least in build 8251 it was). But it seems it's back in some recent builds (maybe from 8664 or newer).