Early, and honest about it.

SSL/TLS with password login, folders from the server, sync on start and every 10 minutes, offline search.

Not yet: STARTTLS for IMAP, downloading mail older than the first 300 per folder, instant push (IDLE).

Reading, flagging, moving and deleting reach the server. Changes wait in a queue that survives restarts and lost connections.

SMTP over SSL/TLS or STARTTLS, an Outbox that retries, and a copy of every sent message in Sent on the server.

Not yet: Attaching new files, Bcc, drafts on the server.

Rendered in a sandbox where no script can run. Remote images stay blocked until you allow them, per message or per sender, and Telex fetches them itself.

Not yet: Style sheets inside messages, opening attachments.

A Sorting Office: rules that sort, flag, move and auto-reply, run on arrival or on demand, each leaving a note on the message.

Not yet: Regular expressions, conditions on headers and attachments, rules that forward.

OAuth2 sign-in, since both refuse plain passwords over IMAP.

Several identities per account, each with its own signature and reply and forward templates. A reply is from the address it was sent to.

Not yet: Greeting templates for new messages, HTML signatures.

Automatic updates and a code-signed installer.