5.7.703: Blocked by your own Tenant Allow/Block List
Exchange Online returns 5.7.703 when someone in your own organization sends to an address or domain that is blocked in your Tenant Allow/Block List. The whole message is blocked for every recipient, even if only one recipient matches a block entry. An admin in your tenant must remove the entry.
The exact message
Microsoft 365 / Exchange Online
5.7.703 Your message can't be delivered because messages to XXX, YYY are blocked by your organization using Tenant Allow Block List.
Why it happens
- An admin in your organization blocked the recipient address or domain.
How to fix it
- Ask your Microsoft 365 admin to review the Tenant Allow/Block List in Microsoft Defender.
- Send separately to the unblocked recipients.
If you send cold email
If a prospect’s domain is on your own block list, a colleague probably added it for a reason. Check before removing it.
How WarmHawk handles it
WarmHawk sends through your own Google Workspace or Microsoft 365 mailboxes. When the provider stops accepting a mailbox’s sign-in (approval removed, password reset, no Exchange Online license), WarmHawk marks that mailbox as needing a reconnect and says why, instead of showing it as connected while every send fails. How WarmHawk works →
Related bounce codes
Sources, checked 2026-09-29: Microsoft Learn: NDRs and SMTP errors in Exchange Online. Have a different bounce? Paste it into the decoder →
Questions
5.7.703 questions
What does 5.7.703 mean?+
Exchange Online returns 5.7.703 when someone in your own organization sends to an address or domain that is blocked in your Tenant Allow/Block List. The whole message is blocked for every recipient, even if only one recipient matches a block entry. An admin in your tenant must remove the entry.
Is 5.7.703 a temporary or permanent error?+
Permanent. The message will not be retried, and sending it again unchanged will fail the same way until the cause is fixed.
How do I fix 5.7.703?+
Ask your Microsoft 365 admin to review the Tenant Allow/Block List in Microsoft Defender. Send separately to the unblocked recipients.