How can Enterprises send bulk marketing emails (80,000+ emails)?

Frequent Contributor

Hello All, Looking for the solution to send bulk emails. I understand, By default, all mailboxes have a 10,000 email per 24 hours send limit to prevent spam. However, our marketing team runs a campaign every fortnight to send out average 80,000 emails. As Office365 doesn't allow, I`m wondering if the following options are correct? Option 1) Create a Distribution List with maximum 5000 users, follow the same to create up to 16 Distribution groups. Thus, the marketing team can send the email to the 16 distribution groups, which in turn will send it to 80,000 (5000 users * 16 = 80000 emails) Option 2) Use 3rd Party solution (please recommend the leading and trusted ones) Option 3) Exchange Hybrid Server Option 4) Linux based mail relay server Any pointer will be deeply appreciated. Thanks

10 Replies

Hi @Admin O365,


We have several customers using option 1 and 3 and it's working has expected.

Use *anything* other than O365, as you risk getting your entire tenant blocked. Whether it's a 3rd party or home-grown solution, depends on multiple factors, so it's up to you to decide. But don't even try to use O365 as a bulk-messaging tool, unless you want to spend hours on the phone trying to restore proper mail flow.

Many 3rd party solutions are out there, i would highly recommend using those. You not only get delivery of your messages but you get full tracking and campaign capabilities so you can get click tracking, open rates (although these are mostly worthless) spam anaylitics all kinds of things you get when using a 3rd party product vs. using an exchange server where you really don't get any analytics and your doing blind marketing.
As others have said, I would recommend not trying to send these using Office365 directly as the account sending the messages could be tagged as sending outbound spam and thus blocked. The trigger for that is not just quantity of mails but also content from what I have experienced.

If you already have a hybrid configured, or other mail relay available that is an option but it really sounds like using a 3rd party service that is designed for this sort of mass marketing is your best bet.

Hi Nuno,


So Option 1 (Distribution Group) to send bulk mail is fine

Just reconfirming as havent tested if O365 will allow to send 80000 emails but technically felt that seperation by having multiple Distribution groups can do the magic.

@Vasil Michev, further update - 


Agreement to use 3rd party to send out emails (mostly nailing down to SENDGRID)


As no Exchange On-premise server, because migrated all mailboxes to Office365 and Exchange servers are decommissioned.

In such case, looking at SMTP relay that will be used to forward the mail to SENDGRID.



a) Onpremise Application that will be sending bulk emails, not sure if recommended to directly configure the SENDGRID details on the appplication. 

Looking at security standpoint, wont that affect or expose the application server (port 25 only allowed, but worried if system can be compromised)?


b) If SMTP gateway used, such as LINUX system with SMTP relay do you see any issue or point of advice.


Thanks in advance.




The dangerous way, if you choose not to go 3rd party.
One thing you can try is to build something to meter the mail that is being sent out. If you can keep it at around 9K emails an hour and let the app push the emails through you mail server, making sure you switch "from" addresses every 20 (rate limit for each email address per minute I think) emails as well.
That would require your organization to set up enough email addresses to handle the total number of emails you want to send, noting that number should never exceed 24. 

I found a few apps like sendblaster that you can use the free version to get a "spam score" on the email that is being sent out, to ensure you aren't doing anything that is going to out you on a spam radar.

@Vasil Michev I plan to use O365 (word+excel+outlook) to send bulk mail (5000/day). Will this cause problem?

you should use a service like sendgrid or some large support function like that to send that many emails, otherwise you run the risk of getting caught in spam traps and having your domain blacklisted.  @Admin O365 

I hear you! We're a large school district and we have to send messages to 70K+ parents in one fell swoop. We can blacklisted all the time. One option we've used is mail metering through an appliance list barracuda. Messages get delayed but it limits getting marked as SPAM (it still happens, though).
The problem is, we could easily be sending 2.1M+ emails in a month if we sent 70K+ messages every day.
3 years late to the message board, but the problem is still relevant. I'm surprised Azure doesn't have a solution for this.