Will p=reject block my own mail?

Only if a legitimate sender of yours is not passing SPF or DKIM with alignment. That is why you start at p=none and read the reports before tightening.

Where do I publish a DMARC record?

As a TXT record at _dmarc.yourdomain.com.

Do I need DMARC if I only send a little email?

It still protects your domain from being spoofed in phishing, and providers increasingly expect it, so yes.

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DMARC record checker

Enter your domain to read its DMARC policy and see whether it protects you, and whether you are set up to receive reports.

What DMARC adds

DMARC builds on SPF and DKIM. It tells receivers what to do when mail claiming to be from your domain fails both checks (none, quarantine or reject), and where to send reports so you can see who is sending as you.

Gmail and Yahoo now require a DMARC record from anyone who sends in bulk, so a missing record is no longer just a missed protection: it can hurt delivery.

The three policies

p=none only monitors. Nothing is blocked, but you start receiving reports. p=quarantine sends failing mail to spam. p=reject refuses it outright. The usual path is to publish p=none with a reporting address, read the reports for a few weeks to find legitimate senders you forgot, then step up to quarantine and finally reject.

The pct tag lets you apply the policy to only part of your failing mail while you build confidence. Leaving it below 100 permanently means part of the spoofed mail still gets through.

Reports and subdomains

The rua tag is where aggregate reports are sent, as a mailto: address. Without it, DMARC is working but you cannot see anything. Subdomains inherit the parent domain's policy unless you set sp= to override it; the checker tells you when the record it found belongs to the parent.

Frequently asked questions

Will p=reject block my own mail?: Only if a legitimate sender of yours is not passing SPF or DKIM with alignment. That is why you start at p=none and read the reports before tightening.
Where do I publish a DMARC record?: As a TXT record at _dmarc.yourdomain.com.
Do I need DMARC if I only send a little email?: It still protects your domain from being spoofed in phishing, and providers increasingly expect it, so yes.