What is an A (Address) record?
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You've probably seen an A record mentioned in your DNS settings and wondered what it actually does. And if you're setting up email, you might have wondered whether it affects delivery at all. The short answer is yes, but not in the way most people expect.
An A record (short for Address record) is a DNS entry that maps a domain name to an IPv4 address. That's it. It's the record that tells the internet "this domain name lives at this IP address." When someone types a domain into a browser, DNS looks up the A record and returns the IP so the browser knows where to connect.
A basic A record looks like this:
tidalmail.com. A 192.0.2.1
That line says: when anything asks where tidalmail.com is, send it to 192.0.2.1.
Where A records matter for email
MX records point to a hostname, not directly to an IP. Something like mail.tidalmail.com. That hostname then needs its own A record to resolve to an actual IP address. So the chain looks like this: MX record points to a hostname, A record maps that hostname to an IP, mail gets delivered there. Break the A record and inbound mail can fail, even if your MX record looks perfectly fine.
A records also matter for webmail access. If your team logs into webmail at something like webmail.tidalmail.com, that subdomain needs an A record pointing to your mail server's IP.
And some SPF configurations use A record lookups to verify that a sending IP belongs to your domain. It's less common than referencing IPs directly, but it's valid syntax and worth knowing about.
A records vs AAAA records
A records handle IPv4 addresses (the four-number format like 192.0.2.1). AAAA records do the same thing for IPv6 addresses, which use a longer format like 2001:db8::1. Most email infrastructure still runs on IPv4, but modern setups often publish both. IPv6 is covered properly in the next question.
Now one thing to keep in mind: a misconfigured A record is unlikely to stop outbound email entirely, but it can absolutely break inbound delivery, webmail access, and some authentication lookups. If something feels broken and you can't point to an obvious cause, checking your A records is a reasonable early step.
If you're debugging a DNS issue and not sure where to start, our free SOS hotline is there for exactly this. No pitch, just help.
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