Hello,
Yes, for this purpose you need to modify the Property Pattern that defines constraints for the Email property. By default, the constraints are defined by the built-in User Pattern.
To modify the User Pattern to accept the plus ('+') character in email addresses:
- Launch Adaxes Administration Console.
- Expand the service node that represents your Adaxes service.
- Navigate to Configuration \ Property Patterns \ Builtin.
- Select the User Pattern.
- Double-click the the Email property.

- In the edit field for the Must match regexp option, specify the following regular expression:
^[a-zA-Z0-9_.%\-\+]+@([a-zA-Z0-9_\-]+\.)+[a-zA-Z0-9_\-]+$

- Save the Property Pattern.
In the next version, the builtin User Pattern will accept the plus ('+') character in email addresses by default.