# Fix email authentication for digicert.com

You are working on the DNS and mail configuration for digicert.com.
Measured by MailAuthWatch on 18 Oct 2026 from public DNS. Grade A (95/100).
Report: https://www.mailauthwatch.com/check/digicert.com

## What is published right now (do not assume anything else)
- SPF (TXT digicert.com): v=spf1 include:%{i}._ip.%{h}._ehlo.%{d}._spf.vali.email include:mktomail.com include:em2881.digicert.com ~all   — valid, 3 of 10 lookups
- DMARC (TXT _dmarc.digicert.com): v=DMARC1; p=quarantine; rua=mailto:dmarc_agg@vali.email,mailto:dmarc@digicert.com
- DKIM: selector1._domainkey (2048-bit), selector2._domainkey (1024-bit), s1._domainkey (2048-bit), s2._domainkey (2048-bit), mail._domainkey (1024-bit), zendesk1._domainkey (2048-bit), zendesk2._domainkey (2048-bit), m1._domainkey (1024-bit)
- MX: digicert-com.mail.protection.outlook.com  → Microsoft 365
- Nameservers: ns20.digicertdns.com, pdns196.ultradns.net …  → DNS host not recognised

## Tasks, in order of impact
### 1. 3 DKIM keys are 1024-bit.
Why: Selectors selector2._domainkey, mail._domainkey, m1._domainkey are under 2048 bits, which some receivers already downgrade. 
Rotate to a 2048-bit key at the sending service.

## Rules
- Publish exactly one SPF record; never add a second v=spf1 TXT.
- Do not remove any include: or ip4: you cannot account for; mail may depend on it.
- Do not set DMARC to p=reject in one step; stage through p=none → quarantine → reject.
- Show the planned DNS changes as a diff (record, old value, new value) before applying them.
- If you cannot access the DNS provider or Microsoft 365, stop and say exactly what access you need.

## Verify
  dig +short TXT digicert.com
  dig +short TXT _dmarc.digicert.com
Then open https://www.mailauthwatch.com/check/digicert.com?fresh=1 and confirm:
  the grade is unchanged and no new issues appear. Target grade: A.

## Report back
List each record you changed (name, type, old value, new value), what you verified, and anything you could not do.