Blocking Distribution lists from becoming JIRA user accounts

[Duke Torbert]

When emailing issues in many of my customers have internal distribution lists that they have asked use to email. This creates a user account in JIRA, which results in multiple JIRA updates being sent to customers. 

Is there away only allow updates to be sent once ?

Is there away to block distribution lists from becoming "Customer"/User account?

Is there away to only allow "approved" customer accounts to receive emails ?

Some other way of blocking these distribution lists from being recorded in JIRA ?

[Nathan Trout]

I'm having this problem as well. The user's name isnt included in the distro list but it's somehow being attach to a temp account with the user's name. 

The weird thing is, the user doesnt show up in the admin directory, just when I @ the user within a ticket. 

[Nic Brough -Adaptavist-]

Why is your Jira email included in distribution lists?  It shouldn't be in them.