To let Fastmail send as you, add include:spf.messagingengine.com to your SPF.
On your domain, for manual DNS setups. Fastmail’s manual-DNS guide documents the record ending in ?all; once DMARC shows all your mail aligned you can choose ~all. Measured on 5 Nov 2026, the include costs 1 of your 10 SPF lookups, leaving 9 for everything else.
- Include
- spf.messagingengine.com
- Vendor’s record
- v=spf1 include:spf.messagingengine.com ?all
- Where it goes
- Your domain’s SPF record (@)
- Needed on your root?
- Yes, if you send through it from your domain
- Lookups (measured)
- 1 of 10
- Ranges published
- 3 ip4 · 0 ip6
- Category
- Mailbox provider
What include:spf.messagingengine.com expands to live, 5 Nov 2026
v=spf1 ip4:103.168.172.128/27 ip4:202.12.124.128/27 ip4:204.75.18.128/27 -all
Counted as RFC 7208 §4.6.4 does: the include itself plus every nested include, a, mx, ptr, exists and redirect. Includes can change at any time; this page re-measures daily.
Adding it next to another service
A domain has exactly one SPF record, so add the include to the record you already have. With Google Workspace, for example:
v=spf1 include:_spf.google.com include:spf.messagingengine.com ~all
DKIM for Fastmail
CNAMEs fm1, fm2 and fm3 ._domainkey (and mesmtp._domainkey) as listed in Fastmail’s manual DNS guide.
How it affects DMARC
DMARC passes when SPF or DKIM passes for a domain aligned with your From address. With Fastmail sending from your domain, its include lets SPF pass and align; DKIM signing with your domain gives you a second, forwarding-proof way to pass.
Other mailbox provider services
Sources
- Fastmail: Manual DNS configuration · checked 5 Oct 2026
- RFC 7208 §4.6.4: DNS lookup limits · checked 5 Oct 2026
peekip isn’t affiliated with Fastmail; follow the vendor’s own setup page, which shows the exact values for your account.