Slack email authentication
Workspace invitation and notification mail.
SPF record
Add Slack to your domain's SPF record with this include:
include:_spf.slack.com
A complete record for a domain sending only through Slack:
v=spf1 include:_spf.slack.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.
Live record
This is what _spf.slack.com published when this page was generated:
v=spf1 -all
DKIM
Enable DKIM inside Slack 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 Slack 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.