Perhaps I should also add that DeltaChat is really just an email client with a user interface that is optimized for chat, and the chatmail servers are just IMAP/SMTP mail stacks optimized for DeltaChat.
DeltaChat uses AutoCrypt to provide gpg/pgp encrypted “email” + metadata, and the chatmail servers are set up to refuse unencrypted messages (thus avoiding the spam problem).
The optimal experience is acheived by using DeltaChat the way it was intended: DeltaChat to DeltaChat communication, and I'd say that using the chatmail servers is also preferable to using custom IMAP/SMTP servers (whether they are hosted by the big providers, smaller providers, or self-hosted). You _can_ use DeltaChat to communicate to email-only recipients, but it provides for a sub-optimal experience.
DeltaChat uses AutoCrypt to provide gpg/pgp encrypted “email” + metadata, and the chatmail servers are set up to refuse unencrypted messages (thus avoiding the spam problem).
The optimal experience is acheived by using DeltaChat the way it was intended: DeltaChat to DeltaChat communication, and I'd say that using the chatmail servers is also preferable to using custom IMAP/SMTP servers (whether they are hosted by the big providers, smaller providers, or self-hosted). You _can_ use DeltaChat to communicate to email-only recipients, but it provides for a sub-optimal experience.