When sending Mishloach Manos, does the Mekabel need to receive it in his hand or can I leave it on his doorstep etc.?
It is OK to leave it at the doorstep, but one must be sure that they are getting it on the day of Purim.
ראה ערוך השולחן סימן תרצ”ה סעיף ט”ז.
Note: The above is only regarding fulfilling the actual Mitzvah of Mishloach Manos. However, if you are giving Mishloach Manos to (at least) one person in a regular way, the restriction above does not apply while giving to others.