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DKIM selector finder

Not sure which selector a domain signs with? This sweep checks 30 common selector names concurrently and reports every DKIM key it finds.

The selectors we check

Selectors can be any name, so no sweep can be exhaustive — this list covers the defaults of the major providers and the names that turn up most often in real DNS. For domains that match a known provider (for example outlook.com), provider-specific selectors are added automatically.

Generic and default selectors

Names many mail servers and DKIM guides use out of the box.

  • default
  • mail
  • dkim
  • dkim1
  • dkim2
  • x
  • smtp

Short numbered selectors

Common at providers that keep two keys published for rotation.

  • s1
  • s2
  • k1
  • k2
  • key1
  • key2

Microsoft 365

Exchange Online publishes selector1 and selector2 as CNAME records.

  • selector1
  • selector2

Google Workspace and Yahoo

Google Workspace uses "google" by default; Yahoo names keys after their length.

  • google
  • yahoo
  • s1024
  • s2048

Other well-known providers

iCloud Mail (sig1), Fastmail (fm1–fm3), Proton Mail, Zoho, and Mailchimp Transactional (mandrill).

  • sig1
  • fm1
  • fm2
  • fm3
  • protonmail
  • protonmail2
  • protonmail3
  • zoho
  • mandrill

Date-based selectors

Providers that rotate keys often name selectors after a date. We check two examples; your provider may use others.

  • 20230601
  • 2023

When a sweep finds nothing

A clean sweep does not prove a domain has no DKIM — it only means none of the common selectors are published. Many organisations use custom or date-based selectors (s202607, mail2026) that no list can predict. The reliable way to find the selector in use is to look at real mail: send yourself a message from the domain, open the raw headers, and read the s= tag inside the DKIM-Signature header. Then confirm the record with the DKIM checker.

Selector naming, why providers publish several keys at once, and how date-based rotation works are all covered in DKIM selectors explained.

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