After long time, I have found few minutes (ok, hour and something…) to test one idea I had. It is not long ago, when we switched our Exchange from older version to version 2010. Because I am using Windows Mobile 6.5 on my phone, I have noticed the new possibility to synchronize SMS from/to mobile with exchange/outlook. Bingo! If I am able to create the item in outlook from within NAV (and yes, I am able, I can create emails etc.), I can send SMS from NAV in this way. Easy!