If I recall correctly this was an issue at launch when they wrongfully banned some crafters that were sending items to friends/family to sell for them.
Since then SE has become more careful though I assume - I've never heard of them wrongfully banning crafters/anyone for such a thing again.
And I've been constantly sending my friends leve-quest-items through the mail, demanding they'd clear their mail box half way through because it was full and no one ever recevied any kind of warning there.