Hi,

Mail in Qatar is delivered majorly to Post Boxes. Ensure that your friend provides you their correct P.O Box Number.

Their address should be something like this:
Name,
Sponsor Company / Sponsor
P.O. Box: (number)
Doha/Wakra/ (insert which part of Qatar they are in)
State of Qatar

Q-Post have gotten better with time, as my colleagues have mentioned to me. Do try it.. Postcards are a lovely way of staying in touch!