Problems sending mass email using Cloud-based O365 Distribution Lists

Question

We have an Office 365 A1 license.  I have created 19 Global email Distribution lists (not personal lists) to allow only a few specific employees to have the rights to send messages using these defined groups. The groups are broken down by employees attributes/departments, etc. We also have a group that contains ALL employees (1300 members), which gets most of the use. The first issue we are having is that the email recipients seem to be limited to 500 users when I run a message trace. These groups range from 5 to 1300 users in size. If the recipient list has more that 500, it seems to be truncated at the 500 user limit.  I didn't think Distribution Lists were supposed to be limited as if I was manually inputting 500+ users in the CC: or BCC: fields.

Answer 1

Hi OCC_Admin, 

Sorry for the misunderstanding. I mistakenly thought that you are using the distribution list (Contact Group). As you are using distribution group, and a distribution group that is stored in the organization's shared address book counts as one recipient, generally speaking, the message can be sent successfully. We’d like to collect the latest whole NDR (non-delivery report) and message trace for further investigation via the private message. You can just click the following link to get the private message. Thanks for your time.

https://answers.microsoft.com/en-us/privatemessage/inbox

Best regards,

Coldwell

Answer 2

Coldwell,

These 19 groups are distribution groups that I created in AD Users & Computers.  If I add one of the named Dlists (ie:  all_******@name.com) (and it has 1300 users in the list) in the BCC: line, shouldn't the message NOT be subject to the "normal" 500 users send limit in O365? 

Dean

Answer 3

Hi OCC_Admin, 

I tried to search the related information about the sending limits across Office 365 options, I find that the recipient limit for Exchange Online is 500 recipients. You can refer to the following picture and link get the details.

https://docs.microsoft.com/en-us/office365/servicedescriptions/exchange-online-service-description/exchange-online-limits

For the purposes of the recipient limit, a distribution group that is stored in the organization's shared address book counts as one recipient. In distribution list, each recipient is counted separately. So, this is a normal behavior that you are unable to send emails to recipients above 500. Given this situation, we suggest that create and use distribution groups instead.

https://docs.microsoft.com/en-us/exchange/recipients-in-exchange-online/manage-distribution-groups/manage-distribution-groups

Best regards,

Coldwell

Answer 4

Hello OCC_Admin

My name is Parmi, I am an Independent Advisor. Thank you for posting your question. I'll be happy to help.

You are pretty much under the limit as per A1 license and this article --- https://docs.microsoft.com/en-us/office365/serv...

I would recommend you to contact O365 Admin support to check your tenant from backend and fix the issue you have as this seems more specific to your tenant.

Contact support for business products - Admin Help

https://docs.microsoft.com/en-us/office365/admi...

Office 365 support

https://support.office.com/home/contact

Let me know if I can help you further!

Regards,

Parmi