The compose window opens in one of two ways: from the Write button in the left sidebar (a fresh letter), or from the Reply link at the foot of any letter (which pre-populates To, Subject, and the quoted body).

§ The header

From
Auto-selected from the received address. Override via the dropdown.
To
One or more addresses, comma-separated. Tab to leave the field.
Cc / Bcc
Hidden by default; click to reveal.
Subject
Plain text. Re: is prepended automatically on replies.
New letterDraft saved · 2s ago
Frompress@book-tour.co ▾
press@book-tour.covia studio
anna@practice.lawvia partners
hello@field-notes.mailvia dispatch
Totypesetter@moraine.co
SubjectRe: Proofs for the spring catalogue

Martin,

The kerning on the title is tight — can we give the subtitle a hair more room before…

📎 0 attachmentsSend ↵
Fig. 03·The compose window, with the From dropdown open. Picking an identity switches DKIM keys as well.

§ Formatting

Select any text to summon a small bubble with bold, italic, and link. Or use the shortcuts ⌘B / ⌘I / ⌘K. The shape on disk is markdown — type **bold**, *italic*, [text](url), or start a line with > for a quote or - for a list, and your letter goes out as a properly-rendered HTML email with the plain markdown source as a text fallback. Paste a URL onto a selected word and it becomes a link in one move.

§ Attachments

Drag files onto the compose window, or use the paperclip in the footer. Each letter carries up to 7 MiB of attachments total, and no individual file can exceed 7 MiB — the mail service accepts a 10 MiB message once encoded, and attachments grow by about a third in encoding. Storage is included and not metered by plan today; we limit single-letter weight to keep delivery predictable.

Warning

Executables (.exe, .bat, .cmd) are rejected outright — most mail servers would bounce them anyway. Zip them if you must.

§ Signatures

Each identity can carry its own signature. They're set from /app/domains/<fqdn>, one per domain, and are appended automatically below your reply with an -- separator (mail convention; clients like Apple Mail and Gmail will render them correctly as signatures, not quoted body).

§ Sending

Hit Send and the letter is handed to SES, DKIM-signed in the domain's own key. A toast confirms delivery. If the address is malformed or the recipient's domain rejects the envelope, the toast turns the colour of a ledger entry in the red — and the letter drops into Drafts with the reason attached so you can fix it and try again.