slack.com

Live email deliverability and anti-spoofing audit. Every value below was read from public DNS at the moment this page was generated.

86/100 — Solid configuration with a few gaps worth closing. Accepts mail · Protected against spoofing · Hosted by Google Workspace

Findings

dkim

No DKIM key found at any common selector. Either DKIM is not configured, or it uses a custom selector we cannot discover from DNS alone.

Fix: Enable DKIM signing at your mail provider and publish the selector they give you.
mta sts

No MTA-STS policy, so inbound mail can be downgraded to an unencrypted connection.

Fix: Publish _mta-sts.slack.com and host a policy at https://mta-sts.slack.com/.well-known/mta-sts.txt.

Mail is handled by Google Workspace.

1 aspmx.l.google.com, 5 alt1.aspmx.l.google.com, 5 alt2.aspmx.l.google.com, 10 aspmx2.googlemail.com, 10 aspmx3.googlemail.com

spf

SPF is published and enforcing.

v=spf1 include:_spf.qualtrics.com include:mail.zendesk.com include:_spfextra.slack.com -all

dmarc

DMARC is enforcing with p=reject.

v=DMARC1;p=reject;fo=1:d:s;pct=100;rua=mailto:dmarc_agg@vali.email,mailto:0e5a5c34@inbox.ondmarc.com;ruf=mailto:0e5a5c34@inbox.ondmarc.com

MX	`1 aspmx.l.google.com` `5 alt1.aspmx.l.google.com` `5 alt2.aspmx.l.google.com` `10 aspmx2.googlemail.com` `10 aspmx3.googlemail.com`
SPF	`v=spf1 include:_spf.qualtrics.com include:mail.zendesk.com include:_spfextra.slack.com -all`
DMARC	`v=DMARC1;p=reject;fo=1:d:s;pct=100;rua=mailto:dmarc_agg@vali.email,mailto:0e5a5c34@inbox.ondmarc.com;ruf=mailto:0e5a5c34@inbox.ondmarc.com`
DKIM selectors	none discovered
MTA-STS	not published
TLS-RPT	not published
BIMI	not published
DNSSEC	validating

Run this check in your own code

Same data, as JSON, in one request. No SMTP probing, no stored recipient data, 250 free calls a month.

curl "https://mailgrade.dev/v1/domain?domain=slack.com"

Also available: /v1/verify?email=… for individual addresses, and /v1/verify/batch for lists.