You do a /search for the person, click on their name, pick the middle (2nd) option out of the three that appear, then hit enter once the message appears in the text box at the bottom.
Then the other person must hit the first "OK" on the mail and they will be added. But to have 'extra features' have the other person do the same as what you just did. Then when you get the mail, you hit the first OK at the top.
Thats always how I did it ;o
(sorry if its confusing

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