XML Error with Exchange Distribution List over 10,000

Trying to send to an Active-Directory based distribtion list of more than 10,000 which will not send?

This type of list has to be expanded by the PoliteMail using Exchange EWS, when using the PoliteMail Server tool to expand the list, to see an unexpected XML error when the list fails to expand fully.

When this occurs, it is because of a mixed 32-bit, 64-bit Exchange and/or Entra ID Tree environment. This limits EWS to a 10k distribution list or less.

The solution is simply to use multiple sub-lists within the To: field, of less than 10k each. In other words, instead of sending to one “AllEmployee” list of say 25,000, you would instead send to 4 lists, say one for each department each being less than 10k total.