Domain and server checks.
What we check every day, what each result means, and how to fix it.
Open Mailboxes, then click a domain. You see its bounce rate, its DNS records and Deeper checks. We run these checks every day.
What we check
| Check | Good | What to do if not |
|---|---|---|
| Spamhaus domain blocklist | Not listed | Stop sending from the domain. Request removal at check.spamhaus.org. |
| Domain age | 30 days or older | Wait. Until then we send at most 10 a day. |
| SPF DNS lookups | 10 or fewer | Remove includes you don’t use. |
| DKIM key size | 2048-bit | Create a new 2048-bit key with your provider. |
| DMARC policy | p=quarantine or p=reject | Start with p=none, then move to p=quarantine. |
For SMTP mailboxes we also check your provider’s sending servers:
- Reverse DNS: each server’s address should have a name, and that name should point back to the same address.
- Spamhaus: the server’s address should not be on a blocklist.
Google, Microsoft and Zoho manage their own servers, so we skip this for them.
What to fix
Below the checks, What to fix lists each problem in plain words, in order. Fix them from the top.
Colors
- Green: fine.
- Amber: works, but could be better.
- Red: fix this. It hurts your delivery.
- Grey: not checked yet.
Alerts
If your domain or your provider’s server gets onto a Spamhaus blocklist, we email the account owner. The mailbox card also shows “On a Spamhaus blocklist”.
If the blocklist row says “Not set up yet”
The blocklist check isn’t running yet. All other checks still work.
Still stuck? Use the chat button inside the app, or email us at [email protected].