What does an MX lookup show for cold email?
MX records name the servers that receive email for a domain, each with a priority number; the lowest number is tried first. A lookup tells you which mailbox host a domain uses (for example Google Workspace or Microsoft 365) and whether the domain can receive mail at all. The checker also catches a null MX, a single 0 . record that tells the world the domain accepts no email.
Does a cold email sending domain need MX records?
Yes. A sending domain must receive the replies to your cold email and the bounce messages that tell you an address is dead. Without MX records, replies have nowhere to go, and some receivers treat a domain that cannot receive mail as a sign of a throwaway sender. Our guide to sending domains covers the full setup.
What MX records do Google Workspace and Microsoft 365 use?
Google Workspace domains set up since 2023 use a single record, smtp.google.com; older setups list the aspmx.l.google.com family, which still works. Microsoft 365 uses a host ending in mail.protection.outlook.com. Copy the exact values from your host's setup screen rather than from a guide, since a typo means lost replies. See Google Workspace for cold email.
Can I use an MX lookup to check a prospect's cold email address?
Partly. A domain with no MX records cannot receive mail, so any address on it will bounce. A domain with MX records can still reject a single address that does not exist, so an MX lookup is not address verification. Our guide to email verification explains the full check, and the domain checker tests SPF, DKIM and DMARC too.