A mailbox that has stopped receiving anything at all is actually one of the easier email problems to diagnose, because it narrows the possible causes considerably compared to "some emails don't arrive" — work through these checks in order rather than guessing.
Step 1: Confirm It Is Actually "Nothing," Not "Some Things"
Ask the sender to resend and watch whether it bounces back to them with an error, or simply disappears silently. A bounce message is diagnostic gold — it usually states the exact reason (mailbox full, domain not found, message rejected) in plain text. A silent disappearance with no bounce points toward a filter or forwarding rule quietly redirecting mail rather than a delivery failure.
Step 2: Check the Mailbox Quota
A full mailbox is the single most common cause of "receiving nothing," and it is entirely self-inflicted: once storage hits its limit, new mail bounces back to the sender rather than queuing. Check current usage against your plan's quota (5GB and 30GB are WebsNP's standard Business and Enterprise tiers) and clear old attachments or archive to free space immediately if you're near the ceiling.
Step 3: Verify the MX Records
MX records tell the internet which server handles mail for your domain. A recent DNS change, domain transfer, or hosting migration can leave stale or missing MX records, which causes mail to bounce as undeliverable at the sending server before it ever reaches you. Check your domain's current MX records against what your email provider actually expects (available in your provider's setup documentation) using any public MX lookup tool.
Step 4: Check for a Forwarding Rule or Filter Silently Redirecting Mail
A forwarding rule set up months ago (sometimes by a former employee, sometimes accidentally) can quietly send all incoming mail to another address with no visible trace in your inbox. Check your mail client's filter and forwarding settings specifically for any rule that redirects or auto-deletes incoming mail, not just the ones you remember creating.
Step 5: Check Whether Your Domain or IP Is Blacklisted — for Outbound, Not Inbound
This one is commonly misunderstood: a blacklisted sending IP affects your outgoing mail's ability to reach others, not your ability to receive mail sent to you. If the problem is specifically incoming mail not arriving, a blacklist check on your own domain is usually a dead end — the fault more likely sits with MX records, quota, or a filter as above.
Step 6: Check Greylisting Delays
Some receiving mail servers apply greylisting — a deliberate temporary rejection of first-contact mail, expecting a legitimate server to retry within minutes while spam senders usually don't. If a specific sender's first message never arrives but a retry a few minutes later does, greylisting on the sender's end (not your own configuration) is the likely explanation, and it resolves itself on retry.
If None of These Resolve It
At that point the fault is more likely server-side on your provider's infrastructure (a service outage, a misapplied server firewall rule) than something in your own configuration — this is where a support ticket with the specific symptom ("nothing arriving, no bounce, MX confirmed correct, quota confirmed under limit") gets a real diagnosis faster than a vague "email isn't working" report.
A Quick Reference Table
| Symptom | Most likely cause |
|---|---|
| Sender gets a bounce with an error | Check the bounce text first — it usually names the exact reason |
| Sender says it sent, nothing arrives, no bounce | Filter/forwarding rule or MX misconfiguration |
| Only one specific sender's mail is missing | Possible greylisting on their end, or a filter targeting their address |
| Nothing from anyone, sudden onset | Full quota or a recent MX/DNS change |
