365 Distribution lists for media mailing lists

[Matt_MobiusNZ]

I have a client with an aging Exchange Server. For years they've run regional distribution lists for their 3.5K members.

Basically we have an organisational unit for each region and then contacts in each OU for each member. 

Then we have dynamic Distribution lists that include all contacts in Each OU.

From there we use the Limited Allowed senders to allow external authorised senders to email the regions so the server will send their email to all members in each region.

It looks like we can do similar on 365 - Make a bunch of contacts and add them to distribution lists.

From what I've read each address book distribution list is only counted as one recipient for the sender.

What are the limits for the outbound mail when sending to the Distribution lists? The most they'd send in a day would be one email to all regions so 3.5K emails. I guess they might very occasionally do it twice to correct an error or something so maybe 7K emails. A lot of the time its just individual regions being emailed.

Will this work - I've found lots of talk of the limits but not really a definitive answer for sending to distribution lists. 

I've suggested Mail Chip but they really want to use existing mail clients to send the emails due to user tech limitations and its member information and isn't related to selling or marketing so they don't require the click / read information of something like mail chimp.

Does this sound like it'll work - We'll then be updating the lists from time to time pragmatically (Powershell or API's) to keep them relevant to their membership database.

Any help greatly appreciated as what I'm finding in documents online is often contradictory.

[#2]

Hi @Matt_MobiusNZ,

https://docs.microsoft.com/en-us/office365/servicedescriptions/exchange-online-service-description/e...
"For distribution groups stored in an organization's address book, the group is counted as one recipient. For distribution groups stored in the Contacts folder of a mailbox, the members of the group are counted individually."

This same article notes that "Exchange Online customers who need to send legitimate bulk commercial email (for example, customer newsletters) should use third-party providers that specialize in these services."

Thanks, Ash

[#3]

I saw that very document. The problem is that indicates that we can send an email to a distribution group and have Microsoft deliver to the members and it only counts as one recipient. I think I can take from them that a group with under 1000 members is fine - There are message size limits which is ok. From there I can see it looks like each person can send to up to 10,000 recipients per day but 1000 at a time (Unless is a distribution group in which case its counted as 1 receipient???).

It seems like I'm just going to have to try it but that requires importing thousands of contacts into my tenancy to test and sending them all a test message and checking delivery reports as for me there is far too much ambiguity.

Then it closes with the bit you have about third party providers. So that indicates they discourage using 365 to send newsletters which in a way this customer is but its a Not for Profit organisation and the membership is tiny by US standards so I figure they can.

Sometimes some cut and dry examples would be useful.

Has anyone actually done this successfully.

[#4]

As a test you could create a distribution group with 2 contacts in it and customize the recipient limit to 1 on the sending mailbox. That would save you importing all contacts until you know it would work.
From the same doc you have read "You can customize recipient limits between 1 and 1000 for existing mailboxes and for new mailboxes that will be created in the future. Edit the recipient limit on existing mailboxes individually or in bulk using the Exchange admin center and customize the default setting for new mailboxes via Remote PowerShell. For more information, see Customizable recipient limits in Office 365."

[#5]

True I guess that would at least test the truth of the Distro List = 1 Recipient bit.
I've created a distro list containing external contacts and allowed certain external senders and that worked that I could email the distro list from my Gmail and the email went to the two external contacts ok.

I suppose once I know about the distro list = 1 recipient thing there is enough to indicate that it will be fit for our purpose. To the client it seems like a lot of emails but in the scheme of international companies and marketing its actually a pretty small number.