OpenPGP, PGP client plugins, applications (related to email clients) - how is the file decrypted?

Question

Programming

I would like to hear from pgp experts how files added to through the mail client are decrypted. For example outlook pgp. From the mail server I receive the source text of the letter, and everything that is related to attachments is, for example, the header "x-content-pgp-universal-saved-content-type" - where is the mime type of the attachment stored, it is not always the same as needed, sometimes it's just octeat-stream, I get the extension from it.
But how do client plugins, applications parse such encrypted attachments and restore data about their name, extension? I can’t get it out of the text of the letter, so there is something of my own, but what?

Answer 1

I will answer myself - when unpacking files, use the "--list-packets" option,
for example "gpg --list-packets test.gpg"
or "gpg --verbose --decrypt test.gpg > NUL"
original answer