Fastmail email authentication
Independent paid mailbox provider with strong custom-domain support.
SPF record
Add Fastmail to your domain's SPF record with this include:
include:spf.messagingengine.com
A complete record for a domain sending only through Fastmail:
v=spf1 include:spf.messagingengine.com ~all
What it costs you
1 of your 10 DNS lookups. That is the cheapest an include can be — the record it points at contains only IP ranges, with no further includes to follow. Behind it are 2 IP ranges.
Live record
This is what spf.messagingengine.com published when this page was generated:
v=spf1 ip4:103.168.172.128/27 ip4:202.12.124.128/27 -all
Domains using Fastmail
Found while resolving 293 well-known domains on 2026-08-04 — each authorises
spf.messagingengine.com in its published SPF record:
DKIM
Enable DKIM inside Fastmail and publish the selector record it generates. DKIM matters more than SPF for deliverability, because a DKIM signature survives forwarding while SPF does not — see how selectors work.
DMARC
Neither SPF nor DKIM protects the address your recipients actually see until DMARC ties them
to it. Once Fastmail is authenticating, publish a DMARC record — start at
p=none with a reporting address and
tighten from there.
Check it worked
DNS changes take minutes to hours to propagate. Once published, run the domain through the checker — it resolves the full include chain and reports the real lookup count.