Safe Sender being blocked by Outlook

If the sender is already on the Safe Senders list and messages still are not arriving in Classic or New Outlook, the most likely cause is that the messages are being filtered before they reach the mailbox.

For Classic Outlook, Safe Senders does not always override server-side filtering:

1. In Classic Outlook, verify the sender or domain is still in Home > Block > Junk E-mail Options > Safe Senders or Safe Recipients.
2. If this is a group or mailing list, add it to Safe Recipients as well, not only Safe Senders.
3. If the mailbox is hosted on Exchange or Exchange Online, Safe Senders changes made in Classic Outlook may not be recognized by Exchange or Exchange Online. In that case, messages can still end up blocked or treated as junk.

For Outlook on the web or Outlook.com settings, add the sender there as well:

1. Open Outlook on the web.
2. Go to Settings > Mail > Junk email.
3. Add the sender address or domain under Safe senders and recipients or Blocked or allow, depending on the interface.
4. Select Save.

Important checks:

• If this is a mailing list or group address, use Safe Recipients for the group address.
• The server that hosts the mailbox can block messages before they ever reach the mailbox, so nothing appears in Inbox or Junk.
• If senders receive a rejection mentioning authentication problems such as SPF failure or access denied, that must be fixed by the sender’s mail system. This is not corrected from Outlook settings.

If the messages are not in Inbox or Junk in any Outlook client, that indicates mailbox-level or server-side filtering rather than a local Outlook block list issue.

References:

• Block or unblock senders in Outlook
• Block or allow (junk email settings)
• Why am I not receiving emails from certain senders that I haven't blocked? - Microsoft Q&A
• Not receiving most emails all of a sudden - Microsoft Q&A