We must be excited to have you apply

Hello everyone,

From the book Hug Your Haters by Jay Baer:

Discover Financial Services participated in a remarkable exchange on their Twitter feed in March 2013 that epitomizes this nimbleness. Rob Speciale (@RobSpeciale) from Austin, Texas, sent a tweet that read:

Haven’t checked my mail in a few days, and there are 3 offers for the @Discover card. Persistence, or lack of coordination?

Within nine minutes, Discover responded with a tweet of its own:

@RobSpeciale We must be excited to have you apply! DM w/ your full name & full address if you would like the mailings to stop.*Amy

Does “We must be excited to have you apply” mean “We are glad that you have applied” or “We will be glad if you apply”?

Thank you.

’To have someone do something’ means to cause someone to do something.
In your example, they demonstrate their nimbleness by tweeting, “We must be excited to cause you to apply!’ (= we’re definitely excited at the prospect of you applying). Referring to the future of course.

Thank you, Eugene.

Eugene, could I ask you one more thing about this Twitter exchange?

Does “DM w/ your full name & full address if you would like the mailings to stop” sound polite and natural to you?
To me it’s like “Hey, if you don’t want to receive our e-mails, give us your full name and address!”
Or do I misunderstand the meaning or register of the phrase?

I don’t think the original is grammatically acceptable.

“We must be excited to have you reply” doesn’t make any sense, even though I think Eugene is correct about the meaning of ‘to have’ here. It should be
“We are excited to have you reply.”
Alternatively it is possible that it should be
“We must be exciting to have you reply”.

You are correct about the meaning of “DM w/ your full name and address.” Appalling!

Thank you, Beeesneees.

Perhaps grammar wasn’t the author of the book’s concern there—he was just using the exchange as it unfolded. Over there in Texas, why bother about the small matter of grammar?
I have to confess though, the original didn’t grate on my ears and still doesn’t (‘apply’ used intransitively, as in: Are you applying?)
Having stumbled upon multiple modals, can you be 100% sure of anything?

The author was quoting a tweet. I’m sure the author, himself, paid attention to grammar.