Your verification report shows over_quota for sales@company.com. Is the address dead? Should you delete it?
No. Over quota means the inbox exists — it's just full. That's a fundamentally different signal from invalid (doesn't exist) or catch_all (can't confirm).
What SMTP Tells Us
When a mail server responds to our RCPT TO probe with codes like:
552 Mailbox full452 Insufficient storage552 Over quota
…the address is real. The recipient (or their IT admin) needs to clear space — not you deleting the lead.
Over Quota vs Other Statuses
| Status | Mailbox exists? | Can receive mail now? |
|---|---|---|
| valid | Yes | Yes |
| over_quota | Yes | No — full |
| invalid | No | No |
| catch_all | Unknown | Unknown |
Over Quota vs Rate Limited
Customers sometimes confuse over_quota with internal rate limiting.
| over_quota | rate_limited (hidden) | |
|---|---|---|
| Cause | Recipient mailbox full | Our SMTP pool busy |
| You see | over_quota |
unknown |
| Billable | Yes — real SMTP answer | No |
| Fix | Retry send in 30–90 days | Re-verify in minutes |
We intentionally show and bill over_quota because you received a definitive SMTP classification worth paying for.
What Should Marketers Do?
- Don't delete over_quota contacts from CRM
- Pause active campaigns to those addresses
- Retry in 30–90 days (mailbox may be cleared)
- Segment separately from invalid/bounce lists
For signup forms: consider allowing registration (inbox exists) but flag for follow-up.
Technical Detection
Our classifier matches quota markers in SMTP responses:
over quota, mailbox full, exceeded storage, quota exceeded, inbox is full
Results are cacheable — re-checking within TTL returns the cached verdict without another SMTP probe.
Credits & Billing
over_quota consumes 1 credit — same tier as valid and invalid. Inconclusive free statuses (catch_all, risky, unknown) remain free.
Verify any address — Single Check →
Related: All Statuses Explained