Exchange Online Management Scope Syntax

The RecipientRestrictionFilter parameter specifies the filter to apply to recipient objects. When the RecipientRestrictionFilter parameter is specified, only server objects that match the filter are included in the scope. If you use the RecipientRestrictionFilter parameter, you can't use the DatabaseRestrictionFilter or ServerRestrictionFilter parameters.

User mailbox is not a server object but GROUP is.
Try to add users you want use in filter to some group and use Group as parameter

Example for Group SalesForce

SET-ManagementScope "SCOPE1" -RecipientRestrictionFilter {memberofgroup -eq "CN=SalesForce,OU=Groups,OU=xxx,DC=xxx,DC=xxx,DC=com"}

Then why does it work if I include only 1 email address in the command?  For example:

Set-ManagementScope "Scope1" -RecipientRestrictionFilter { EmailAddresses -Eq 'user1@company.com' }

so try replace -or with -and

That just replaces the "-or" with "-and" in the field.  It's as if it is just placing the exact text of the command into the field rather than actaully populating the addresses.

I know that with group is working so just try,, create group, add those 2 members and use group syntax

When looking at the result of Get-ManagementScope | fl should the content of the RecipientFilter field be formatted EmailAddresses -eq 'smtp:user1@comapny.com' or should it just show the actual address?

Where should the group be created?  (This is O365 Exchange Online).

Should I create a security group in the EAC, and then add the users there?

It's exchange based so i think it will be distribution group.
It's even better for you because if you decide replace user in script you don't have to run script again, just replace user in group

I think that is about security group. I'm not sure because I can;t test it right now but if you going to use "CN=SalesForce,OU=Groups,OU=xxx,DC=xxx,DC=xxx,DC=com" i think is pointing to active directory

How do I reference the group in the command?  You said "CN=SalesForce,OU=Groups,OU=xxx,DC=xxx,DC=xxx,DC=com", but I'm wondering in this case if just 'group@company.com' would work?

Thanks Chris:  After your comment I re-applied my original PS command.  For some reason it looked wrong to me when view from the Get-ManagementScope | fl output, but apparently I had just not waited long enough for the settings to take effect before testing.  :(

The original syntax actually works fine.

Tom:  Thanks for your input as well.  I appreciate the help.  (I was pretty sure there was a way to do it with the filters I was working with; I just needed a bit more patience I guess.  :)

I've spend a lot of time to try to help you and no assisted solution from you, Thank You

Tom:  Please do not take offense.  I am grateful for your assistance, but I'm not sure that your recommendations were really an "assisted solution"?  You said that my original method would not work when, in fact, it does.  I'm not downplaying your effort or technical expertise.  I'm merely trying to reflect the actual solution for the benefit of anyone who may later view this question.  If I have handled this incorrectly I apologize.  If any other experts would like to comment I am happy to re-assign the points -- if that is possible?  Or else, perhaps a moderator can do so?