this is related to http://www.atlassian.com/software/jira/docs/latest/issue_creation_email.html

we have multiple projects on our server, each of which has an email address which users can send mail to and create a defect report in that project.
The problem is that createusers only creates a standard set of permissions regardless of the e-mail address the user sent to.
(i.e. the new user is added to whatever groups are defined for Administration --> Global Permissions --> JIRA Users )

What we need is a way that a user sending to proj_A@myCompany.com is created as a member of the groups jira-users and projectA-users,
while a user sending to proj_B@myCompany.com is created as a member of the groups jira-users and projectB-users.

We need this due to the privacy concerns that some of our customers have for their products (which we develop for them).

Note that this is somewhat related to http://jira.atlassian.com/browse/JRA-10364 but not exactly, since some of our customers prefer to use their personal e-mail addresses when creating accounts.

While there may be cleaner ways to resolve this, one possible way occurs to me:
the developer would optionally define another handler parameter when using the createusers=true parameter. let's call is additionalgroup for the sake of example.

the ProjectA_Service would have handler.params defined similar to: .... createusers=true, additiaonalgroup=projectA-users, catchemail=proj_A@myCompany.com ....

the ProjectB_Service would have handler.params defined similar to: .... createusers=true, additiaonalgroup=projectB-users, catchemail=proj_B@myCompany.com ....

both of these services would pass their respective additionalgroup values to the service that actually creates the user in Jira.
As a result , the JIRA Users permission under Global Permissions would only include the jira-users group.