Microsoft 365 432 4.3.2
STOREDRV.Deliver; recipient thread limit exceeded
Microsoft 365 432 4.3.2 means: sTOREDRV.Deliver; recipient thread limit exceeded. It is a temporary failure, so your server retries it. The fix is in the sending or receiving configuration named above, not in the list. Fix that, then resend.
Microsoft 365’s exact wording
Quoted from Microsoft Learn: Email non-delivery reports and SMTP errors in Exchange Online, checked 2026-11-05. Placeholders are Microsoft 365’s own.
Provider's description
STOREDRV.Deliver; recipient thread limit exceeded
Possible cause
The ability of the recipient mailbox to accept messages is throttled because it's receiving too many messages too quickly. Throttling is done so that a single recipient's mail processing doesn't unfairly affect other recipients who are sharing the mailbox database.
| Who sends it | Microsoft 365, Exchange Online and Outlook.com |
|---|---|
| Basic code | 432: A password transition is needed (RFC) |
| Enhanced code | 4.3.2: System not accepting network messages |
| Permanent or temporary | Temporary (4xx) |
| Verifying the list prevents it | No |
What the sender should do
The fix is in the sending or receiving configuration named above, not in the list. Fix that, then resend.
Would verifying the list have prevented Microsoft 365 432 4.3.2?
No
This reply is about your sending setup, the message or the receiving system, not about whether the address exists, so verifying the list will not prevent it.
Common questions
- What does Microsoft 365 432 4.3.2 mean?
- Microsoft 365 432 4.3.2 means: sTOREDRV.Deliver; recipient thread limit exceeded. It is a temporary failure, so your server retries it. The fix is in the sending or receiving configuration named above, not in the list. Fix that, then resend.
- Should I retry after Microsoft 365 432 4.3.2?
- Your sending server retries it automatically, because it is a temporary (4xx) failure. Investigate only if it keeps coming back over several hours.
- Would verifying my list have prevented Microsoft 365 432 4.3.2?
- No. This reply is about your sending setup, the message or the receiving system, not about whether the address exists, so verifying the list will not prevent it.
Sources
- Microsoft Learn: Email non-delivery reports and SMTP errors in Exchange Online (checked 2026-11-05)
- IANA: SMTP Enhanced Status Codes registry (checked 2026-11-05)
- RFC 4954: SMTP Service Extension for Authentication (checked 2026-11-05)
Registry and provider wording is quoted exactly; guidance is written by the SimpleVerifier Team.
SimpleVerifier Team · Last checked against the sources 2026-11-05