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Built on JMAP — the modern mail protocol
IMAP is from 1986. Your phone wasn't. Reeva runs natively on JMAP, the open standard that finally drags email into the present — fast incremental sync, real push, JSON over HTTPS. And yes, we still speak IMAP and SMTP for every legacy client you own.
What is JMAP?
JMAP (JSON Meta Application Protocol) is an open IETF standard for mail, calendars and contacts. It was designed at Fastmail and standardised in RFC 8620 (the core protocol) and RFC 8621 (mail-specific bits).
Where IMAP is a stateful, line-based protocol that pretends your inbox is a filesystem from the 1980s, JMAP is a stateless JSON API over HTTPS that treats email like the API surface it actually is. You ask "what changed since state X?" and get a diff. You ask "give me the first 50 messages matching this filter, with these properties only" and get exactly that — in one request.
It is not a Reeva extension or a vendor trick. JMAP is an open spec, with multiple independent server implementations ( Stalwart , Cyrus, Fastmail's own) and client libraries in every major language. Pick another JMAP provider tomorrow and your data migrates with a single API call.
Why JMAP wins
Six concrete advantages over IMAP — for you, your battery, and the network between you and your mail.
Faster sync
JMAP fetches what changed since your last sync in a single round-trip — no per-folder polling, no FETCH 1:*. Opening Reeva on a phone after a week away takes one request, not hundreds.
Real push, no polling
Native PushSubscription delivers new mail to clients the moment it lands. Your battery stops paying for the privilege of checking an empty inbox every 60 seconds.
Batched operations
Move 200 messages, mark them read, and apply a label — one HTTP call. IMAP needs hundreds of commands for the same job, each blocking the next.
A protocol from this decade
JSON over HTTPS, OAuth-ready, queryable like an API. IMAP shipped in 1986 and shows it — every modern feature is a workaround bolted on top.
Server-side search that actually works
Query by subject, sender, body, attachment name, date range — combined and paged on the server. No more downloading mailboxes locally to grep them.
Same encryption, less leakage
JMAP runs over TLS 1.3 with the same crypto guarantees as IMAP. The protocol metadata is smaller, so observers see less about your usage patterns.
The receipts
Same task, two protocols. Look at the round-trips.
IMAP — "what's new?"
a1 LOGIN user pass
a2 LIST "" "*"
a3 SELECT INBOX
a4 UID FETCH 1:* (FLAGS)
a5 SELECT Sent
a6 UID FETCH 1:* (FLAGS)
a7 SELECT Archive
a8 UID FETCH 1:* (FLAGS)
... one SELECT + FETCH per folder ...One request per folder. State lives on both ends. A laptop coming back from sleep with 20 folders = 40+ round-trips before showing one new message.
JMAP — same question
POST /jmap HTTPS
{
"using": ["urn:ietf:params:jmap:mail"],
"methodCalls": [[
"Email/changes",
{ "accountId": "u1", "sinceState": "42" },
"0"
]]
}One HTTPS call. The server replies with the exact set of message IDs that changed since your last sync, across every folder, in JSON you can parse in three lines.
Use it from any client
Native JMAP where we can, IMAP / SMTP everywhere else. Bring whatever you already use — nothing locks you in.
Reeva apps
Web, desktop, mobile
Thunderbird
JMAP add-on (or IMAP)
Apple Mail
IMAP fallback
K-9 Mail
IMAP fallback
FairEmail
IMAP/JMAP via add-on
Stalwart CLI
Server admin
We still speak IMAP, SMTP, CardDAV and CalDAV
Bragging about JMAP isn't an excuse to lock you in. Every Reeva mailbox is also reachable over IMAP4rev1 for incoming mail, SMTP-AUTH for sending, CardDAV for contacts and CalDAV for calendars. Use Apple Mail, Outlook, Thunderbird, mutt — anything. Your data, your client choice.
Email from this decade. Free to try.
Encrypted email on JMAP, calendar, contacts, password vault and cloud — one account, no tracking.