Add IMAP to Snappymail for external accounts and alternate Indentities to write from

Summary

Services like Proton and Titan offer a really nice import from Gmail and other mail service providers to pull, but then then also offer the ability when owning an domain to write from that email through their service. I am proposing a way to meet that without the hard work of doing the import but instead to use the same feature in the Android Mail service to sync with the Snappymail service or to at least offer the ability to use an alternate non-murena email.

Description

I currently have a website that I have the email address from and would like to keep that email address for the identity with that website.

A great use case is maintaining, existing emails that are unrelated to murena that might be a business account or a non-personal account in the same place across devices.

A user has existing contacts and communication from their website that uses their domain and they wish to still send. As much as we degoogle, others dont and we still need access to google accounts, instead of going to google email service it would take us off of that requirement and keep it in the Murena ethos.

Reflection

I understand that there might be more calls to an from the murena email services and the others, which may complicate bandwidth, maybe limit those syncs to be more manageable.