Your use of mailto:'@annotation()' selected all joinpoints in program execution where the subject of the joinpoint has the specified annotation.
When your program runs there is a method-call joinpoint to your annotated method followed immediately by a method-execution joinpoint for your annotated method. If you change the advice to print the joinpoint object, you will see these two joinpoints.
What you need to do is select which joinpoint you are interested in. Probably method-execution in your case: