Use your "messages" app on the iPad instead. That way you'll know when the recipient has received your message. I use it instead of email on my iPhone also. Otherwise, as Harry stated, you won't get a return receipt.
There's a way to do it for Mail in OS X, but not in iOS, as far as I know. As chaps said, it's pretty archaic, and, with a small exception of some government service departments, setup to acknowledge by default, all but useless. I had it disabled (i.e. went back to Apple's default) about two years ago ...
Speaking for myself, I always deeply resented return-receipt-requested emails. To me, they are shouting "PAY ATTENTION TO ME NOW! I'M MORE IMPORTANT!!" which naturally elicits exactly the opposite reaction in me and into the bin they go!
It used to be pretty standard practice in corporate world, harking back to the times, when one would telephone immediately after sending a fax, to confirm a safe, i.e. legible, receipt ...
Some government service departments set to email receipt acknowledgement automatically, whether requested by sender or not - just the other day, I got one from the local Council Tax office, and that's to one of my private accounts, which never had return receipt request enabled in the first place.
This is a second thread in as many days, making me feel sufficiently dinosaur-ish, whereby something I always took for granted, revealed to be neither obvious, nor universally accepted, if slightly archaic, practice ...
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