MX record

A DNS record that names the mail servers accepting email for a domain, each with a preference number: lower numbers are tried first.

A sending server looks up the MX records of the recipient’s domain and delivers to the host with the lowest preference value, moving to the next one if it does not answer. With no MX record at all, delivery falls back to the domain’s A or AAAA record (RFC 5321). A domain whose MX hosts do not exist cannot receive mail, which is why list checks look them up. MX says where mail arrives; SPF says who may send it.

Share: LinkedIn · X ·

Related terms

Null MX record: A DNS record (MX 0 .) that says a domain accepts no email at all (RFC 7505), so senders give up at once and list checks can drop its addresses.
SPF (Sender Policy Framework): A DNS record listing which servers may send email for your domain.
Hard bounce: A permanent delivery failure: the address or its domain does not exist or refuses mail.

← All terms

Need this built, fixed or reviewed?

I build and rescue products with AI coding agents under rules: AI features in production, honest estimates, email that gets delivered.

Book a free 30-min call See price and start date

How I work

Przemysław Zalewski · 15+ years shipping software

“a true bias for action” client CTO, public LinkedIn recommendation

Confidential by default. NDA is standard. I never show your project, name or screenshots without written consent, which is why this site names no clients without permission.
Your code, your accounts. Code and data stay in your repository and accounts. AI tools run with training on your data turned off, and secrets never reach a model.
A handover you can use. Every project ends with the same checklist: a README that gets it running, one architecture diagram, written decisions, CI, a runbook and a recorded walkthrough. It is done when someone outside the project can run it from the docs.
Boring technology where it counts. I pick a stack you can hire for. Anything experimental needs your yes and an exit plan.
Approach matched to your risk appetite. Prototype, product or regulated: the level decides how much autonomy the agents get and how much review and validation each change needs.
Everything checkable. Every number on my pages links to its source. My tools are free, and the idea validator skill is open source (MIT).

All principles and risk levels →