Is there a way to make a Security List in Active Directory not also act as a Distribution List?
"Like distribution groups, security groups can also be used as an e-mail entity" (Active Directory)
Only if you attach an e-mail address to a group will it appear in outlook.
Right click > 'Exchange Tasks', there can you add or remove a group's e-mail address, has to be done on an Exchange Server.
A distribution group is only used by e-mail software and cannot be used when setting permissions.
A security group however can be used both for setting permissions and as a target for e-mail software. To my knowledge this behavior cannot be changed.