@MarieIVanArkleStinks
Deeply unpleasant thread. I never think twice about the numerous women who text DH, both colleagues and friends. Of course in most people's world that's fine. But I agree there's something 'off' about this. She's messaging a near stranger out of the blue demanding favours: that's strange in itself, especially when the favour isn't even necessary and it would be easy to simply have a courier deliver the parcel.
He's said no and she's still pestering: a person she barely knows. Muriel's right: she has no boundaries and people like this do invariably end up being more trouble than they're worth. If he is revelling in the attention to wind her up, I'd also suggest he needs to grow up.
As to what you do about it I don't know, but agree that interfering with your partner's phone isn't it. But I'd not be even slightly happy if my DH handled this kind of situation in this way. YANBU.
Agree with this. And I also agree it is a deeply unpleasant thread with - as I said, and several others have said - the usual nasty, scornful responses, (response number 25, 'you sound unhinged' has now been deleted thankfully.)
I agree with @MilesOfSand who said 'all the cool girls are on here for us to admire!' even though their post has been mocked and laughed at. Although, I strongly believe that they are only 'cool girls' on mumsnet, and in real life, they'd go fucking batshit if the same situation was occurring with their husband. And I agree with a few posters that the OP's husband is revelling in the attention.
@Mojitoqueen I'm out, as I can't stand the nasty comments aimed at you on here, and anyone defending you. If I were you, I would ask mumsnet to delete this thread as it's not going to get any better, and it's not going to help you. Too many people on it who enjoy kicking someone when they're down.... All the 'crying with tears of laughter' emojis and mocking and taunting..... Nasty as fuck. 
As I said, I'm out. Hope this thread is deleted soon.