unable to send emails to a group of people

bill jones 0 Reputation points
2026-09-12T17:31:56.8333333+00:00

I have been trying to send minutes of a meeting to twelve people and i keep getting message from postmaster general saying that they have failed to be delivered

Outlook | Web | Outlook.com | Email
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  1. AI answer

    2026-09-12T17:32:12.54+00:00

    Check the non-delivery report from the postmaster and look for the "Diagnostic information for administrators" section. That section usually states why delivery failed.

    For a message sent to 12 people, the most likely fixes supported here are:

    1. Verify each recipient address
      • Open the message again.
      • In the To box, delete each recipient address that may be wrong.
      • Start typing the address and, if it appears in Auto-Complete, remove the old suggestion.
      • Re-enter the full address carefully and send again.
      • This helps if one or more saved addresses are outdated or misspelled.
    2. Reduce recipients and test in smaller batches
      • Try sending to 1 to 3 recipients first.
      • If that works, send the remaining recipients in smaller groups.
      • This can help if the send attempt triggered anti-spam protection.
    3. Check attachment size
      • If the meeting minutes include an attachment, Outlook.com cannot send the message if an attachment is larger than 25 MB.
      • Some failed delivery guidance also notes problems when the original message had an attachment larger than 10 MB.
      • If the file is large, upload it to OneDrive and send a link instead.
    4. If the error mentions mailbox full
      • The recipient’s mailbox cannot accept new mail.
      • The message can still be delivered to other recipients.
    5. If the error mentions server timeout, connection timed out, or message expired
      • Wait a short time and resend.
      • These errors often resolve on their own.
    6. If the error mentions blocked, blacklist, spamcop, dynablock, blackhole, or spamhaus
      • The recipient’s mail server blocked the message as suspected spam.
      • The recipient’s email provider support team must unblock the account or domain.
    7. If sending from Outlook or another mail app
      • Try sending the same message directly from Outlook.com.

    If the addresses are correct and the message still fails, check whether the message has a signature and try removing it before resending.

    AI-generated content may be incorrect. Read our transparency notes for more information.

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  2. Hornblower409 14,925 Reputation points
    2026-09-13T07:23:30.1233333+00:00

    @bill jones said

    trying to send minutes of a meeting to twelve people and i keep getting message ... saying that they have failed to be delivered

    If the AI Answer didn't help, please tell me:

    Are you are getting a message back from Microsoft along the lines of ""To help protect users and prevent spam, we've placed a limit on the number of messages you can send"?

    Or is it a Non-Delivery Report (aka NDR, Bounce message) from the recipient's mail server? If so, what is the code (e.g. "550.1") and text ("Suspected Spam") from the report?

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