I have a server setup using Postfix and Dovecot (2.3.16) using maildir format and I have the zlib plugin enabled. I have confirmed compression support works by copying compressed mails over and it can read them ok.
However, it won't automatically compress incoming emails. I have a server with Exim and Dovecot and it compressed incoming mail. It named the mail files with an S=size tag. According to the Dovecot docs, having S=size in the filename is needed for compression but it doesn't say how to add this:
https://doc.dovecot.org/configuration_manual/zlib_plugin/
I tried adding the quota plugins and using dovecot for virtual_transport but incoming mail is still saved without the size info in the filename.
https://mailing.postfix.users.narkive.com/qeccJkBe/configure-mail-filename
How can I configure Postfix or Dovecot to add the incoming mail size to the filename so that it gets compressed?