MX (Mail Exchanger) records tell the internet which servers accept email for a domain. If MX is wrong or missing, mail cannot be delivered reliably — and many verifiers and receivers treat that as a hard failure.
What an MX record contains
An MX record has:
- Priority (preference) — lower number = higher priority
- Host — the mail server name (e.g.
aspmx.l.google.com)
Example shape:
10 aspmx.l.google.com
20 alt1.aspmx.l.google.comSenders try the lowest priority first, then fall back.
How to look up MX records
Use the MX record checker to see live MX hosts and often the provider behind them (Google Workspace, Microsoft 365, etc.).
Pair it with:
- Domain health checker — MX + SPF + DMARC + blacklists
- Email verifier — domains without MX rarely accept mail
Why MX matters for cold email
- Verification — no MX usually means do not send
- Provider detection — different hosts behave differently under volume
- Setup validation — after you point a domain at Google or Microsoft, confirm MX before warming
MX vs SPF vs DMARC
| Record | Role |
|--------|------|
| MX | Where inbound mail goes |
| SPF | Which servers may send as the domain |
| DKIM | Signature verification |
| DMARC | Policy when auth fails |
Inbound routing (MX) and outbound trust (SPF/DKIM/DMARC) are related but not the same. Check both sides when onboarding a domain.
Quick setup checklist for a new outbound domain
- Register domain
- Set MX for your mailbox provider
- Confirm with MX checker
- Add SPF, DKIM, DMARC — authentication checker
- Warm before scale — warmup calculator
If you are standing up many domains at once, doing this by hand gets expensive fast. Send a brief and we will map the full stack to your volume.