Could you please specify your exact problem that you need help with? Did you manage to add a classic email account on your Delta Chat installation? You should still be able to send unencrypted mail via a classic account.
A chat profile using a classic email address allows to to send and receive unencrypted messages. These messages, and the chats they appear in, are marked with an email icon.
Also, could you please share the URL where you read that support for non-chatmail relays will be deprecated? This seems to go around a lot nowadays, and thus needs to be reworded to reduce the chance for misunderstanding.