Bulk email with 500 recipients limit. Options and thoughts.

Usually, the recipient limit in Exchange Online for a mailbox is 500 recipients. Of course, that limit can be modified by the Admins but there are other points to take in consideration:

On the other hand we have the outbound antipsam policy, https://security.microsoft.com/

Even if we increase the recipient limit on Exchange side, if we don't check the outbound antispam policy and adapt it, the user will not be able to send the message with external recipients and will probably be blocked to send messages until the next day. ( An Admin can unblock him/her but that will take some hour ). 

Remove-BlockedSenderAddress -SenderAddress <user email address>

Now the next point... Does the user really need to send messages to more than 500 recipients?

Well... Sometimes yes. But quite always that's something that can be "fixed" using Distribution Lists instead of single recipients.

Ok... But, and if DL isn't an option?

That's a scenario that you'll need to deal with sooner or later.

In that case, you have 2 options... The easy one is to increase the different limits for a group of users, ( in Exchange and in the outbound anti spam policy ). But that will also increase the risk to be identified by third parties as potential spammers.

So, the other option, ( and my preferred one ), is to teach the users how to send bulk messages with the mail merge option.

The users will need their own contacts database, ( this can be a simple Excel sheet as the screenshot below ).

With that file, the user/s can send to them a bulk message from word following this instructions:

https://support.microsoft.com/en-gb/office/use-mail-merge-to-send-bulk-email-messages-0f123521-20ce-4aa8-8b62-ac211dedefa4

This method has many advantages:

- The user/group/office can maintain his own contacts list. Add contacts, remove them or modify them without any request to the IT team.

- The user/group/office will be able to send a message to all them without the 500 limitation, as all the messages will go out individually.

- As all the messages go out individually, there will be no risk that the recipient servers identifies the bulk mail as SPAM.

- This method allows the sender to send out a bulk message to hundreds of users but, at the same time, if desired, personalized for each one with a simple automated variable, ( described in the MS article ).