O365 restrict number of recipients

[Sibrows]

So after a good few hours looking into this, I'm pretty sure this isn't possible but thought I'd check the collective wisdom here . . .

 

I'm looking for a way to either restrict the number recipients students or submit emails with large numbers of recipients for review.

 

6 months ago I restricted the students to stop them being able to send to the larger distribution lists and they've just worked out that they can expand the list and circumvent this restriction.

 

While I would love to rely on sanctions for inappropriate use of the email system, I've been asked to investigate other options.

 

 

1. Options to restrict the max recipient value on the mailbox. This is greyed out and from a bit of Googling isn't adjustable without a paid plan.
   
2. Mail flow rule. There doesn't appear to be a simple option, unless I'm missing it, for 'recipient account greater than'.
   
3. Add a bogus address to the lists they are expanding. Doable but hardly full proof.
   

 

Have I missed anything?

Has anyone found another way around this?

 

Thanks in advance...

 

Simon

[FN-GM]

I used option 1 in the past with DirSync no problem. Even on the free plan.

[Sibrows]

I used option 1 in the past with DirSync no problem. Even on the free plan.

 

Do you know which attribute you set for this to take effect?

[FN-GM]

Not off the top of my head. We have dumped Office 365 now so I can't check either. It will be same as the exchange attribute so if you could find that on Google you should be ok.

[free780]

Are the distribution lists meant for staff. You could change the Gal students are pointed to.

[eyetea]

Could you restrict senders to a specific list / group? Or do you need external / unknown emails to email the distro list?

[BKGarry]

This is a massive in theory moment, but I have not tested this, but these instructions should work in reverse, it seems you set them at the plan level, which means you set the student plan to the amount of recipients you with them to have

 

https://thoughtsofanidlemind.com/2011/10/28/office-365-recipient-limits/

[Sibrows]

Not off the top of my head. We have dumped Office 365 now so I can't check either. It will be same as the exchange attribute so if you could find that on Google you should be ok.

I think I've found the attribute msExchRecipLimit the frustration is that when syncing this value isn't reflected in the Exchange Admin Center. I've submitted a ticket with M$ Support to see if I can get this syncing correctly.

 

Are the distribution lists meant for staff. You could change the Gal students are pointed to.

 

I hadn't considered the GAL, while this would deal with any future I would need to remove any emails with the list expanded in their mailboxes thus far to avoid further 'reply to all'.

 

Could you restrict senders to a specific list / group? Or do you need external / unknown emails to email the distro list?

 

This was my first step but that held the students back for about 6 months until one of them worked out they could expand the list and negate that control.

 

Edited: to remove bizarre formatting from the quotes.

Edited November 14, 2017 by Sibrows

[eyetea]

Apologies - did read that this morning! Pre-caffeinated brain!

[Sibrows]

This is a massive in theory moment, but I have not tested this, but these instructions should work in reverse, it seems you set them at the plan level, which means you set the student plan to the amount of recipients you with them to have

 

https://thoughtsofanidlemind.com/201...ipient-limits/

 

Am I missing something the article finishes with this setting can't be adjusted?

 

Apologies - did read that this morning! Pre-caffeinated brain!

 

No problem - more caffeine is never a bad thing!

[BKGarry]

Am I missing something the article finishes with this setting can't be adjusted?

 

Ah yes. I didn't get a chance to try until I was in and going for the day.

 

I can see it doesn't work, sorry for the red herring there

[BKGarry]

So my Google-Fu has said that the CMDlet

Set-mailbox -RecipientLimits

is only available on Onsite exchange and is not available on exchange online at all.

 

This may be where the stumbling block has occurred :-(

[Sibrows]

So my Google-Fu has said that the CMDlet

Set-mailbox -RecipientLimits

is only available on Onsite exchange and is not available on exchange online at all.

 

This may be where the stumbling block has occurred :-(

 

We've never had on-site exchange but extending the schema in AD allowed for settings like the restriction of who can send to the distribution groups synced from on-site. So I was hoping that something like this would work successfully.

 

It looks like:

Set-mailbox -RecipientLimits

 

sets the value for msExchRecipLimit.

 

Microsoft are due to call me back shortly so I'll update if they have anything to add.

[Sibrows]

So having spent an hour on the phone with Microsoft support this morning.

 

There is no way to achieve this.

The max recipient limit is hardcoded into office365.

 

They told me that it's been submitted as a feature request but after a quick Google it would appear that other educational establishments have been asking for this for 2 years:

https://office365.uservoice.com/forums/289138-office-365-security-compliance/suggestions/9701511-change-exchange-online-recipient-limit

 

I don't hold out very much hope. Thanks one and all for your input.

[chrisjako]

I take it you are talking about them adding single recipient emails addresses in manually, because if its groups of recipients they are spamming you could just easily setup a rule for that

 

I have a user group called 'all students' which obviously all students are a member of, I have setup a rule that when a member from this group tries to email the 'all students' group the email is directed to my inbox for accept or reject authorisation first, I then have the ability to sanction the student based on its content before rejecting it

 

Then a secondary rule instantly rejecting emails sent from anyone within the all students group to any staff based group like the 'finance team' for example

 

This at least elimanates most of the spammy type of emails sent by students

[Victor_Ivanidze]

Google for "RestrictExtRecips for Outlook 365" tool.