MX records and cold email deliverability: the often-forgotten record
SPF, DKIM, DMARC get all the attention. MX is the one that controls what happens to bounces and replies - and it matters more than people think.
Rejwan Nirob·Mar 26, 2026·4 min readMX records tell the world where to deliver mail addressed to your domain. For a sender-only domain - a cold-email burner with no real human checking the inbox - operators sometimes skip MX entirely. That is a mistake.
Why senders need MX
Bounces, auto-replies, and DMARC reports all come back to the From address. If MX is missing or mis-configured, those messages disappear. You lose the bounce signal that warmup tools rely on. You lose the unsubscribe-loop reply path. You lose the DMARC report stream.
Worse, missing MX is itself a deliverability signal. Mailbox providers see a domain with SPF and DKIM but no MX as a one-way blast cannon. They notice.
What good MX looks like for cold email
- Point at a real mailbox provider - Google Workspace, Microsoft 365, Fastmail
- Configure five priority levels matching the provider documentation
- Verify the records propagated using dig MX yourdomain.com
- Process replies - even if it is just an autoresponder pointing at a real address
The Inboxlee default
Every domain we provision ships with the full Google Workspace MX stack - five records, correct priorities, no manual editing. The mailbox is real, replies route to a real inbox, and bounces return cleanly.
Frequently asked
Do I need MX records for sending cold email?
Technically you only need MX to receive mail, not send. But receiving providers check that your domain can also receive mail before trusting your outbound. A domain with no MX or pointing at nothing fails this check and lands in spam disproportionately - so MX matters for inbound reply handling AND outbound trust.
How many MX records should Google Workspace have?
Five, with specific priorities (1, 5, 5, 10, 10) all pointing at Google smtp servers. This is the official Workspace MX stack. Inboxlee provisions this automatically on every domain - no manual configuration.
What happens if my MX records point at the wrong server?
Inbound replies bounce, prospects who hit Reply get an error, and your reply rate is reported as zero - hurting both relationship building AND your reputation score. The receiving server also sees the broken inbound and treats your outbound mail with more suspicion.
Does Inboxlee handle MX setup for me?
Yes. Full Google Workspace MX stack (5 records, correct priorities) applied automatically at domain registration time. Background polling verifies propagation before the mailbox is marked live - typically within 5 to 30 minutes.