Mailbox for customers or new tenant ?

Copper Contributor

Hi there,


I'm growing into Microsoft 365 from my role as a system engineer in a large company, but also as a freelancer taking care of IT for small businesses.


Most of the time when I provide webspace for a customer, a mailbox is included.  Now I'm thinking to give my customers an exchange mailbox (in their own domain).

So to be clear: I have multiple customers which need 1 or 2 mailboxes on their own domain. E.g.;; ...


Now I'm wondering what is the best practice here:

Should I buy Exchange Online (Plan 1) licenses for them, and assign them in my own MS365 tenant ?

Or should I create a new tenant for every customer ?


Can anybody give me some advice about this ?  Pro's, cons, pitfalls ?


Thanks in advance !

4 Replies

Hi @StevenBrs,


As a best practice, each company must have its own Office 365 Tenant and its domain validated there.


If I'm a customer I want to control all of my data regarding where they are and if you are using the same tenant you could have issues with compliance or someone can share their data with other customers that resides on the same tenant.


Best Regards,
Nuno Árias Silva
Office Apps and Services

@StevenBrs Setting up separate tenants is definitely the way to go. Single license tenants are more common than you might think. You can also become a Microsoft Partner. What that means is that one, Microsoft will pay you a percentage of every license sold with you listed as the partner. This would be in addition to anything you chose to charge your customers for acting as an administrator. You can also upsell them on other services like getting MS Office Pro for their business. 
Also if you have enough customers Microsoft will give you a batch of O365 licenses for your partner account for free.

Hi @Nuno Silva and @John_OHalloran ,


Thanks for your answers. I will create new tenants and look into the MS partnership.

Are there any prerequisites to become a partner ? I only have a 365 fundamentals certification and only a few customers that need O365.


Best regards


Hi @StevenBrs,


Here you have more information to how to become a partner. 


Best Regards,
Nuno Árias Silva
MVP Office Apps and Services