Our company like many others has a list of distribution groups for sending emails to various departments and offices within the company. Recenlty I just noticed that all of these distribution groups have an email address associated with them. Doing some testing I found that it is possible to send to the distribution group from outside the company providing you know the email@example.com email address that is associated with it.
This is not good to have as it could potentially allow someone from outside to send mass emails within the company or it could allow for a terminated employee to do the same as well as a whole host of other bad things.
What I would like to do is stop someone from the outside from being able to send to those distribution groups but still be able to use them internally.
Originally I thought that using exchange tasks, and removing the email address would stop the ability to reach it from outside which it did. Now however I can not see the group in my outlook and cant send to it. Maybe im missing something maybe im doing someting wrong but im kinda stumped.