Emails to Contact Lists are showing as SPAM and are unable to be delivered

Question

Emails to Contact Lists are showing as SPAM and are unable to be delivered

Lee Pagan 40

I send emails to 5 Contact Lists for a Support Group.
Recently, the first Contact List will receive the email but the following Contact List emails show as being SENT and then my INBOX shows that the email was unable to be delivered (and lists all of the recipients) due to it being blocked as SPAM. It mentions that the email can be resent but that would add the Recipients Email Addresses in the TO box instead of the BCC.
I have tried to clean out any faulty email addresses plus I also avoid sending too many in one day.
I really need to talk to a person in Microsoft who can help me unblock and fix this problem.
Can anyone help me resolve this problem?
Thank you for the assistance.

0 comments

Answer accepted by question author

Chloe-V 15,075 Microsoft External Staff Moderator

Hi @Lee Pagan

I understand how important it is to send these updates reliably to your support group.

Since the first Contact List receives the message successfully, the issue may involve a particular recipient or the affected Contact Lists. As an additional test, please create a new Contact List containing only two or three active email addresses, then send a short test message from Outlook.com on the web.

If the message is delivered, gradually add the remaining recipients in small groups. This may help identify a problematic address. If the new list works with the same recipients but the original list does not, recreating the affected Contact List may resolve the issue.

I have initiated a Private Message for you. Please send the complete non-delivery report, including the error code and diagnostic information, through the Private Message so we can review it securely.

User's image

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Chloe-V 15,075 Reputation points Microsoft External Staff Moderator

2026-10-21T23:33:36.65+00:00

Hi @Lee Pagan

Thank you for providing the full error message. The code 554 5.7.0 / 550 5.7.520 AS(4810) confirms that the message was blocked because Microsoft’s filtering system identified the email content or sending pattern as potential spam.

Since this occurs when sending to a Contact List, please try sending the message to a smaller number of recipients first. You can also simplify the subject and message body, remove unnecessary links, attachments, repeated wording, or unusual formatting, and avoid sending the same message repeatedly within a short period.

If possible, please also test by sending a new, plain-text email to one or two recipients. This will help determine whether the block is related to the message content or the number of recipients.
Lee Pagan 40 Reputation points

2026-10-22T09:19:52.02+00:00

Thanks Chloe-V
I have tried most of those things and have been able to successfully send to a smaller list (only 4 recipients in the list).
I also tried simplifying the message and removed links, images, etc, but it still wouldn't send.
I usually wait 24 hours before sending the messages to the next contact list but this also hasn't worked.
The initial Contact List that received the group email had about the same number of recipients as the other Contact Lists so that is why I am confused about why that one worked and the subsequent ones haven't.
I struggle with my own health and this has caused additional anguish. I just wish that someone could clear the emails and allow me to send them like I used to do a few months ago. I don't understand what has changed to cause this major issue. I have continued to do what I did in the past and it used to work well (as long as I spread out the emails over a few days or I would receive a reply to say that I had reached the daily quota and that the message was saved in Drafts to send the next day) but now it doesn't work.
Once again, thank you so much for taking the time to help. I really don't know what to do now.
Chloe-V 15,075 Reputation points Microsoft External Staff Moderator

2026-10-22T23:41:08.25+00:00
Hi @Lee Pagan

I’m sorry this issue has caused you additional stress, especially while you are already dealing with health challenges. I understand how important it is for you to communicate reliably with your support group.

Please note that this is a user-to-user support forum. Moderators, contributors including external Microsoft employees cannot directly intervene in Microsoft product features or access back-end systems. Our role is limited to providing technical guidance on reported issues, requests, or ideas only.

Since you have already tested smaller Contact Lists, simplified the messages, removed links and images, and waited 24 hours, the next appropriate step is to contact Microsoft Support so they can review the account and sending restriction more closely.

Go to Contact Microsoft Support.

Select Show expanded list of products.

Select Outlook > Get Home support.

Enter Outlook live chat, then select Get Help > Contact Support.

Sign in with the affected account. If that is not possible, use another Microsoft account to view the available support options.

Ask our Support Assistant > Type "Talk to live chat agent" > Contact Support

Under Products & Services, select Other Products > Outlook, then choose Chat with a support agent in your web browser.

I hope the support team can help clarify why the messages are being blocked.
Peter Sutton 5 Reputation points

2026-10-25T19:29:42.02+00:00

I have a similar question. I have just opened an account which works fine for single emails. I have set a group as I sent emails to 57 members every two weeks. But my first group email has been refused as spam.

There are no bad email addresses as two weeks ago they were all delivered from another email provider who has just ended its email business

How is spam defined - surely there are other people who send out emails to groups
Chloe-V 15,075 Reputation points Microsoft External Staff Moderator

2026-10-25T23:49:16.75+00:00

Hi Peter Sutton

Thanks for sharing the details. Even if all 57 email addresses are valid, a newly created account sending the same message to a relatively large group can still trigger Outlook’s automated anti-spam protections. The system considers multiple factors, not only whether the recipient addresses are valid.

Since regular individual emails are working but the group message is being rejected, I would suggest trying a smaller group first and gradually increasing the number of recipients. If the messages continue to be blocked, please contact Microsoft Support so they can check whether there is a sending restriction associated with the account.

Please note that this is a user-to-user support forum. Moderators, contributors including external Microsoft employees cannot directly intervene in Microsoft product features or access back-end systems. Our role is limited to providing technical guidance on reported issues, requests, or ideas only.

I hope this helps clarify why the group message may have been treated differently.
Peter Sutton 5 Reputation points

2026-10-27T14:55:40.6066667+00:00

Thank you for your comments and hints.

I manages to send up to 9 BCCs, but no more.

Surely the content is either spam or not. I don't understand why 9 is not spam but 10 recipients is spam

This seems to be a very arbitrary process, next time it may well not allow 9 recipients.

If any human read the contents they would see that it was not spam. Has Microsoft put a special marker against this source, and can it be removed?
Peter Sutton 5 Reputation points

2026-10-27T15:03:21.2166667+00:00

I have just contacted Microsoft help, and they have said

"Sorry, there are no results for your issue"
Peter Sutton 5 Reputation points

2026-10-27T15:24:01.2233333+00:00

This is intolerable, Outlook will now only let me send to one blind copy at a time. What is going on?
Lee Pagan 40 Reputation points

2026-10-28T00:05:00.94+00:00

I completely understand your frustration, Peter.
I ended up connecting with a contact support from Microsoft and they ended up telling me that it was a specific Outlook.com issue and gave me steps to contact them. Those steps didn't work and then it all stalled so I didn't get to chat to another support person.
I have simplified the content of my group emails and, about every 2nd day, I make another attempt to send to a Contact List. Usually this fails and I receive notification that it has been marked as SPAM. The crazy thing is that on one day, one of the emails (to 1 of my 5 Contact Lists) suddenly went through! I was ecstatic and believed that the issue had righted itself but, no, it has failed to send to the other lists since then.
I am going to try the steps to Outlook.com again today and hope for a miracle. I need this to work so that I can reach the members in my support group (for gatherings and for participation in research and treatment opportunities).
Chloe-V 15,075 Reputation points Microsoft External Staff Moderator

2026-10-28T23:57:56.91+00:00

Hello

I understand that this issue is still affecting both of you.

As these issues may involve account-level sending restrictions, forum moderators unfortunately do not have access to Microsoft’s back-end systems or the authority to inspect the affected accounts or remove such restrictions.

Please try contacting Microsoft Support again using an InPrivate or Incognito browser window. If you are unable to contact Support while signed in to the affected account, please use a different Microsoft account to initiate the support request. You can then provide the affected account details privately when requested by the support agent.
Peter Sutton 5 Reputation points

2026-11-03T19:59:33.8466667+00:00

Chloe

Many thanks for your comments and help

I have found the solution. I have opened a Gmail account and that works fine.
Chloe-V 15,075 Reputation points Microsoft External Staff Moderator

2026-11-04T01:45:56.7433333+00:00

Hi Peter Sutton

Thank you for the update. I’m glad to hear that you’ve found a solution and that everything is working fine now.

Thank you again for letting us know.

1 additional answer

Your answer

Chloe-V 15,075 Reputation points Microsoft External Staff Moderator

2026-10-21T23:33:36.65+00:00

Hi @Lee Pagan

Thank you for providing the full error message. The code 554 5.7.0 / 550 5.7.520 AS(4810) confirms that the message was blocked because Microsoft’s filtering system identified the email content or sending pattern as potential spam.

Since this occurs when sending to a Contact List, please try sending the message to a smaller number of recipients first. You can also simplify the subject and message body, remove unnecessary links, attachments, repeated wording, or unusual formatting, and avoid sending the same message repeatedly within a short period.

If possible, please also test by sending a new, plain-text email to one or two recipients. This will help determine whether the block is related to the message content or the number of recipients.
Lee Pagan 40 Reputation points

2026-10-22T09:19:52.02+00:00

Thanks Chloe-V
I have tried most of those things and have been able to successfully send to a smaller list (only 4 recipients in the list).
I also tried simplifying the message and removed links, images, etc, but it still wouldn't send.
I usually wait 24 hours before sending the messages to the next contact list but this also hasn't worked.
The initial Contact List that received the group email had about the same number of recipients as the other Contact Lists so that is why I am confused about why that one worked and the subsequent ones haven't.
I struggle with my own health and this has caused additional anguish. I just wish that someone could clear the emails and allow me to send them like I used to do a few months ago. I don't understand what has changed to cause this major issue. I have continued to do what I did in the past and it used to work well (as long as I spread out the emails over a few days or I would receive a reply to say that I had reached the daily quota and that the message was saved in Drafts to send the next day) but now it doesn't work.
Once again, thank you so much for taking the time to help. I really don't know what to do now.
Chloe-V 15,075 Reputation points Microsoft External Staff Moderator

2026-10-22T23:41:08.25+00:00

Hi @Lee Pagan

I’m sorry this issue has caused you additional stress, especially while you are already dealing with health challenges. I understand how important it is for you to communicate reliably with your support group.

Please note that this is a user-to-user support forum. Moderators, contributors including external Microsoft employees cannot directly intervene in Microsoft product features or access back-end systems. Our role is limited to providing technical guidance on reported issues, requests, or ideas only.

Since you have already tested smaller Contact Lists, simplified the messages, removed links and images, and waited 24 hours, the next appropriate step is to contact Microsoft Support so they can review the account and sending restriction more closely.

Go to Contact Microsoft Support.

Select Show expanded list of products.

Select Outlook > Get Home support.

Enter Outlook live chat, then select Get Help > Contact Support.

Sign in with the affected account. If that is not possible, use another Microsoft account to view the available support options.

Ask our Support Assistant > Type "Talk to live chat agent" > Contact Support

Under Products & Services, select Other Products > Outlook, then choose Chat with a support agent in your web browser.

I hope the support team can help clarify why the messages are being blocked.
Peter Sutton 5 Reputation points

2026-10-25T19:29:42.02+00:00

I have a similar question. I have just opened an account which works fine for single emails. I have set a group as I sent emails to 57 members every two weeks. But my first group email has been refused as spam.

There are no bad email addresses as two weeks ago they were all delivered from another email provider who has just ended its email business

How is spam defined - surely there are other people who send out emails to groups
Chloe-V 15,075 Reputation points Microsoft External Staff Moderator

2026-10-25T23:49:16.75+00:00

Hi Peter Sutton

Thanks for sharing the details. Even if all 57 email addresses are valid, a newly created account sending the same message to a relatively large group can still trigger Outlook’s automated anti-spam protections. The system considers multiple factors, not only whether the recipient addresses are valid.

Since regular individual emails are working but the group message is being rejected, I would suggest trying a smaller group first and gradually increasing the number of recipients. If the messages continue to be blocked, please contact Microsoft Support so they can check whether there is a sending restriction associated with the account.

Please note that this is a user-to-user support forum. Moderators, contributors including external Microsoft employees cannot directly intervene in Microsoft product features or access back-end systems. Our role is limited to providing technical guidance on reported issues, requests, or ideas only.

I hope this helps clarify why the group message may have been treated differently.
Peter Sutton 5 Reputation points

2026-10-27T14:55:40.6066667+00:00

Thank you for your comments and hints.

I manages to send up to 9 BCCs, but no more.

Surely the content is either spam or not. I don't understand why 9 is not spam but 10 recipients is spam

This seems to be a very arbitrary process, next time it may well not allow 9 recipients.

If any human read the contents they would see that it was not spam. Has Microsoft put a special marker against this source, and can it be removed?
Peter Sutton 5 Reputation points

2026-10-27T15:03:21.2166667+00:00

I have just contacted Microsoft help, and they have said

"Sorry, there are no results for your issue"
Peter Sutton 5 Reputation points

2026-10-27T15:24:01.2233333+00:00

This is intolerable, Outlook will now only let me send to one blind copy at a time. What is going on?
Lee Pagan 40 Reputation points

2026-10-28T00:05:00.94+00:00

I completely understand your frustration, Peter.
I ended up connecting with a contact support from Microsoft and they ended up telling me that it was a specific Outlook.com issue and gave me steps to contact them. Those steps didn't work and then it all stalled so I didn't get to chat to another support person.
I have simplified the content of my group emails and, about every 2nd day, I make another attempt to send to a Contact List. Usually this fails and I receive notification that it has been marked as SPAM. The crazy thing is that on one day, one of the emails (to 1 of my 5 Contact Lists) suddenly went through! I was ecstatic and believed that the issue had righted itself but, no, it has failed to send to the other lists since then.
I am going to try the steps to Outlook.com again today and hope for a miracle. I need this to work so that I can reach the members in my support group (for gatherings and for participation in research and treatment opportunities).
Chloe-V 15,075 Reputation points Microsoft External Staff Moderator

2026-10-28T23:57:56.91+00:00

Hello

I understand that this issue is still affecting both of you.

As these issues may involve account-level sending restrictions, forum moderators unfortunately do not have access to Microsoft’s back-end systems or the authority to inspect the affected accounts or remove such restrictions.

Please try contacting Microsoft Support again using an InPrivate or Incognito browser window. If you are unable to contact Support while signed in to the affected account, please use a different Microsoft account to initiate the support request. You can then provide the affected account details privately when requested by the support agent.
Peter Sutton 5 Reputation points

2026-11-03T19:59:33.8466667+00:00

Chloe

Many thanks for your comments and help

I have found the solution. I have opened a Gmail account and that works fine.
Chloe-V 15,075 Reputation points Microsoft External Staff Moderator

2026-11-04T01:45:56.7433333+00:00

Hi Peter Sutton

Thank you for the update. I’m glad to hear that you’ve found a solution and that everything is working fine now.

Thank you again for letting us know.

Answer 1

Contact Outlook.com Support through the signed-in Help pane and provide the complete non-delivery report so they can determine whether an outbound restriction has been applied to your account.

Contact Outlook.com Support

Sign in to Outlook.com in a web browser.
Select the ? (Help) icon at the top.
Enter “Messages to contact lists blocked as spam”.
Complete the suggested troubleshooting.
Scroll to Still need help?, select Yes, and choose the available contact option. This is Microsoft’s official Outlook.com support route.^1^
Include:
- The complete delivery-failure message, including its error code and diagnostic section.
- The approximate date and time of the failed sends.
- The number of recipients in each Contact List.
- The fact that the first list succeeds while subsequent lists are rejected.
- A request to check for an outbound anti-spam or sending-quota restriction on the account.

Do not post the diagnostic report publicly without removing email addresses, request IDs, and other account information.

Identify which system is blocking the message

The exact wording in the delivery report determines the correct escalation:

Outbound Outlook.com restriction: If the diagnostic section contains terms such as OutboundSpamException, RefuseQuota, or indicates that Outlook.com refused submission, the restriction is on the sending account. Outlook.com applies daily-recipient, per-message recipient, and non-relationship-recipient limits; actual limits can vary with subscription status and usage history.^2^
Recipient-server block: If the report says blocked, listed in, or names services such as Spamhaus, SpamCop, or another blocklist, the receiving provider is rejecting the message. In that case, the recipients or their email provider must request that the sender/account be allowed.^3^

Because the first Contact List succeeds and later lists fail, an Outlook.com sending restriction is plausible, but the diagnostic text is needed to confirm it.

Safe workaround while support investigates

Do not use the offered resend option if it exposes every member in the To field.

Instead:

Allow time for any temporary sending window to reset before attempting another group message.
Divide each Contact List into substantially smaller batches and space the messages apart.
Avoid placing all recipients in BCC where possible; Microsoft identifies heavy BCC use and high-volume sending as factors that can affect spam reputation.^4^
Send a new, short message from Outlook.com on the web to one or two established contacts:
- If that also fails, add the result to the support case because it points toward an account-level restriction.
- If it succeeds, increase the batch size cautiously rather than resending all five lists.
For recurring support-group announcements, consider a consent-based mailing-list service designed for group distribution. It preserves recipient privacy and manages bulk-delivery controls more appropriately than repeatedly expanding Outlook Contact Lists.

You have already cleaned the lists and reduced daily sending, so repeating address cleanup is unlikely to be the useful next step unless the delivery report specifically identifies an invalid recipient.

References