Please add functions for custom functionality of email message content

Problem/Motivation

Please, add functions for custom functionality which makes communicating with content entities more fluent than it is now.
Simple email functionality is great, but getting an email, deriving actions out of its body/title/... to CRUD fields of content would be fantastic.
There are many modules that enable sending mails. But non that makes CRUDing content from the mails inside mailbox.

So some events to customizing the processing of content->mails and mails2content would be fantastic.

e.g. events for:

before/while checking an email.
after checking an email

checking content marked for transforming into an email
creating an email
after creating an email/before sending an email
...

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes