Lots of stories from those with a happy ending to horror stories.
Lived in Asia for two years have lots of friends with Asian wives and girlfriends, relationships form 1 to 30 years. None met via “mail order” but more than a few met their partners in night clubs but that’s hardly new is it. I have a friend who’s married a Russian girl he met via an I troductory service, so far so good.
Horror stories mostly around money grabbers who’ve stolen money and/or turned very nasty after having a baby. It’s not uncommon for the western husband/boyfriend to be expected to support/help out the girls relations
Hard to generalise but a “mail order / introductory service” wouldn’t work for me and I wouldn’t advise it to anyone else.