Subject: Repeated Outlook Groups calendar spam – meeting invitations appear in calendar despite blocking and mail rules

Question

Subject: Repeated Outlook Groups calendar spam – meeting invitations appear in calendar despite blocking and mail rules

Lieven VDD 20

Subject: Repeated Outlook Groups calendar spam – meeting invitations appear in calendar despite blocking and mail rules

Dear Microsoft Support,

I am experiencing an ongoing issue with my personal Outlook.com/Hotmail account involving unsolicited Outlook Groups and calendar invitations.

Unknown/spam accounts are repeatedly adding my email address to newly created Outlook Groups without my permission. These groups use addresses such as:

******@groups.outlook.com ******@groups.outlook.com ******@groups.outlook.com

Shortly afterwards, I receive fraudulent meeting invitations from these groups. Outlook correctly identifies the messages as spam, but the associated meeting requests still appear in my Outlook calendar and are consequently synchronized to the Outlook calendar on my iPhone.

I have already taken the following measures:

Added groups.outlook.com to my blocked senders and domains.
Created an Outlook rule where Sender address contains @groups.outlook.com → Delete.
Enabled Stop processing more rules for this rule.
Manually left/deleted all unsolicited Outlook Groups from my account.
Despite doing this, new unsolicited groups continue to appear, without my consent.
New meeting invitations from these groups consequently continue to appear in my calendar.

The main problem therefore does not appear to be normal email spam filtering. The meeting invitation seems to be processed by Outlook Calendar even when the corresponding email is identified as spam or deleted by a mail rule.

Could you please investigate the following:

Why can unknown third parties repeatedly add my personal Outlook.com account to Outlook Groups without my approval or consent?
Is there a way to prevent my account from being added to any Outlook Group unless I explicitly accept the invitation?
Is there a server-side setting that prevents meeting requests originating from @groups.outlook.com from being automatically processed by Outlook Calendar?
Why are meeting requests still added/displayed in my calendar when the originating message is classified as spam and matches a deletion rule?
Can Microsoft block this abuse at account/server level, rather than requiring me to continually leave newly created spam groups?
Is Microsoft currently aware of this specific abuse of groups.outlook.com for calendar spam?

This is not an isolated unwanted email issue. New Outlook Groups continue to be created and my account continues to be added to them without authorization, making manual removal ineffective.

I would therefore appreciate it if this case could be escalated to the appropriate Outlook.com / Outlook Groups security or abuse team, rather than only recommending standard junk-email filtering or blocked-sender settings, as those measures are already in place and have not resolved the issue.

I can provide screenshots showing the unsolicited Groups, the @groups.outlook.com senders, the meeting invitations, my blocked-domain settings and the Outlook rules currently configured.

Thank you in advance for investigating this issue.

Kind regards, LievenSubject: Repeated Outlook Groups calendar spam – meeting invitations appear in calendar despite blocking and mail rules

Dear Microsoft Support,

I am experiencing an ongoing issue with my personal Outlook.com/Hotmail account involving unsolicited Outlook Groups and calendar invitations.

Unknown/spam accounts are repeatedly adding my email address to newly created Outlook Groups without my permission. These groups use addresses such as:

******@groups.outlook.com
******@groups.outlook.com
******@groups.outlook.com

Shortly afterwards, I receive fraudulent meeting invitations from these groups. Outlook correctly identifies the messages as spam, but the associated meeting requests still appear in my Outlook calendar and are consequently synchronized to the Outlook calendar on my iPhone.

I have already taken the following measures:

Added groups.outlook.com to my blocked senders and domains.
Created an Outlook rule where Sender address contains @groups.outlook.com → Delete.
Enabled Stop processing more rules for this rule.
Manually left/deleted all unsolicited Outlook Groups from my account.
Despite doing this, new unsolicited groups continue to appear, without my consent.
New meeting invitations from these groups consequently continue to appear in my calendar.

The main problem therefore does not appear to be normal email spam filtering. The meeting invitation seems to be processed by Outlook Calendar even when the corresponding email is identified as spam or deleted by a mail rule.

Could you please investigate the following:

Why can unknown third parties repeatedly add my personal Outlook.com account to Outlook Groups without my approval or consent?
Is there a way to prevent my account from being added to any Outlook Group unless I explicitly accept the invitation?
Is there a server-side setting that prevents meeting requests originating from @groups.outlook.com from being automatically processed by Outlook Calendar?
Why are meeting requests still added/displayed in my calendar when the originating message is classified as spam and matches a deletion rule?
Can Microsoft block this abuse at account/server level, rather than requiring me to continually leave newly created spam groups?
Is Microsoft currently aware of this specific abuse of groups.outlook.com for calendar spam?

This is not an isolated unwanted email issue. New Outlook Groups continue to be created and my account continues to be added to them without authorization, making manual removal ineffective.

I would therefore appreciate it if this case could be escalated to the appropriate Outlook.com / Outlook Groups security or abuse team, rather than only recommending standard junk-email filtering or blocked-sender settings, as those measures are already in place and have not resolved the issue.

I can provide screenshots showing the unsolicited Groups, the @groups.outlook.com senders, the meeting invitations, my blocked-domain settings and the Outlook rules currently configured.

Thank you in advance for investigating this issue.

Kind regards.

Brian A 0 Reputation points

2026-08-28T19:39:18.0233333+00:00

I am posting to echo "Lieven" and thousands of other paid Outlook 365 users suffering from the calendar spam injection exploit. Spammers have found a major loophole using ******@groups.outlook.com

Despite submitting hundreds of diagnostic report recordings directly to Microsoft, nothing has changed. I have spent hours creating rule after rule targeting every possible phrase ("invited you", "shared a photo", "on behalf of" forwarded , on behalf of and many more specific- subject, line, body, headers -etc -etc words and addtional level of blocking ). Outlook rules refuse to catch these, and they won't even clear out of the Junk folder automatically. even when you flag all delete all attachment sent as a folder, links, pictures, folders etc ect. No level of filtering stops these auto launch calanders

Why are premium Microsoft 365 users being left unprotected against a documented infrastructure exploit? We desperately need a native setting that blocks external accounts from auto-joining us to Outlook Groups.com We even tried to remove block in Outlook and Micros.ft 365 Groups.com from our PC (Groups.outlook.com).. Does anyone know a method to remove or restrict internally from a cmd or other command the new Groups.com feature in win11 and Outlook 365?
Hornblower409 14,690 Reputation points

2026-08-30T03:55:58.9833333+00:00

@Brian A said

We desperately need a native setting that blocks external accounts from auto-joining us to Outlook Groups.com

I fully understand your frustration, but posting on an old Q&A thread is not going to be noticed by anyone except the people already following this thread.

All any of us can do at this point is Vote for and Comment on this Feature Request:

Add an option to block being added to Outlook Groups without consent
https://feedbackportal.microsoft.com/feedback/idea/a17de24f-8ce6-f011-92b9-7c1e5244b89c
(You must "Sign In" at the top right of the Feedback page before you can vote).

Answer accepted by question author

Allan Solomon Mejia 8,000

Hello @Lieven VDD

Based on what you've described, I agree that this is not simply a normal junk-email filtering problem.

The important distinction is that Microsoft 365/Outlook Groups have their own membership and calendar behavior. Microsoft documents that when someone is a member/follower of a Group, group meeting invitations can be delivered to the member's inbox and Group calendar activity is handled separately from ordinary email conversations.

That explains why a rule that deletes messages from @groups.outlook.com may not reliably prevent the corresponding calendar item from appearing. The mail rule is processing the message, but it isn't necessarily preventing the Group/calendar service from processing the event.

Microsoft also documents that Outlook.com Group members can leave a Group:

Outlook → Groups → select the Group → Group name → Member → remove yourself/leave the Group.

However, you've already done this, and the significant part of your report is that new unsolicited Groups continue appearing afterward. That isn't something I'd expect you to solve by continually creating mail rules or manually leaving Groups.

For a personal Outlook.com account, I am not aware of a documented user setting that says “require my approval before anyone can add me to an Outlook Group”, nor a supported setting that globally blocks all @groups.outlook.com calendar processing while retaining normal calendar invitations.

Therefore, I wouldn't recommend additional Outlook rules as the primary solution.

I suggest reporting this directly to Microsoft from Outlook.com:

Help → Help → Feedback → Report a problem

Include:

Several examples of the unsolicited @groups.outlook.com addresses
Approximate UTC timestamps
Screenshots showing the Groups appearing without your action
The associated calendar invitations
Confirmation that you've already left the Groups
Confirmation that groups.outlook.com is already blocked and mail rules are deleting the messages
The fact that new Groups continue to be created and your account is repeatedly added

I would specifically describe it as repeated unsolicited Outlook.com Group membership/calendar abuse, rather than ordinary email spam. That distinction is important because junk-mail rules alone aren't addressing the underlying Group membership behavior.

I also don't see a currently published Microsoft advisory confirming this specific groups.outlook.com abuse pattern, so I wouldn't claim that Microsoft has officially acknowledged a service-wide issue at this point.

Given that the unwanted Group membership itself keeps recurring, this likely needs investigation on Microsoft's side rather than further client-side Outlook configuration.

Please "Accept the Answer" if this information helped you. This will help us and others in the community.

Lieven VDD 20 Reputation points

2026-08-29T13:26:10.4766667+00:00

Dear Allen, thanks for your answer: I have reported it to Microsoft directly several times already, well documented and described during several weeks without any feedback unfortunately.

1 additional answer

Your answer

Brian A 0 Reputation points

2026-08-28T19:39:18.0233333+00:00

I am posting to echo "Lieven" and thousands of other paid Outlook 365 users suffering from the calendar spam injection exploit. Spammers have found a major loophole using ******@groups.outlook.com

Despite submitting hundreds of diagnostic report recordings directly to Microsoft, nothing has changed. I have spent hours creating rule after rule targeting every possible phrase ("invited you", "shared a photo", "on behalf of" forwarded , on behalf of and many more specific- subject, line, body, headers -etc -etc words and addtional level of blocking ). Outlook rules refuse to catch these, and they won't even clear out of the Junk folder automatically. even when you flag all delete all attachment sent as a folder, links, pictures, folders etc ect. No level of filtering stops these auto launch calanders

Why are premium Microsoft 365 users being left unprotected against a documented infrastructure exploit? We desperately need a native setting that blocks external accounts from auto-joining us to Outlook Groups.com We even tried to remove block in Outlook and Micros.ft 365 Groups.com from our PC (Groups.outlook.com).. Does anyone know a method to remove or restrict internally from a cmd or other command the new Groups.com feature in win11 and Outlook 365?
Hornblower409 14,690 Reputation points

2026-08-30T03:55:58.9833333+00:00

@Brian A said

We desperately need a native setting that blocks external accounts from auto-joining us to Outlook Groups.com

I fully understand your frustration, but posting on an old Q&A thread is not going to be noticed by anyone except the people already following this thread.

All any of us can do at this point is Vote for and Comment on this Feature Request:

Add an option to block being added to Outlook Groups without consent
https://feedbackportal.microsoft.com/feedback/idea/a17de24f-8ce6-f011-92b9-7c1e5244b89c
(You must "Sign In" at the top right of the Feedback page before you can vote).
Lieven VDD 20 Reputation points

2026-08-29T13:26:10.4766667+00:00

Dear Allen, thanks for your answer: I have reported it to Microsoft directly several times already, well documented and described during several weeks without any feedback unfortunately.

Answer 1

@Lieven VDD said

have reported it to Microsoft directly several times already, well documented and described during several weeks without any feedback unfortunately.

This is a know issue. Microsoft is aware of the problem. There is currently no fix. You can continue to submit Problem Reports, each report moves this issue one tiny bit higher on the Outlook Fixit List.

And I would also suggest that you Vote for and Comment on this Feature Request. If enough people complain, perhaps someone at Microsoft will give this issue the attention it deserves.

(You must "Sign In" at the top right of the Feedback page before you can vote).

Add an option to block being added to Outlook Groups without consent
https://feedbackportal.microsoft.com/feedback/idea/a17de24f-8ce6-f011-92b9-7c1e5244b89c