I have an original iPad mini running iOS 9.3. When sending large eMail attachments, it doesn't ask me if I want to use Maildrop and fails miserably.
My iPhone SE offers me to use Maildrop though
How can I convince the iPad to try Maildrop?
Apple's support page says that the only requirement is iOS 9.2.
Best Answer
First, make sure MailDrop is enabled. I don't own an iPad mini but this may help.
This link points out that only IMAP email accounts had a checkbox to activate the MailDrop/iCloud option.
One thing I noticed is it may not prompt MailDrop but it may still use MailDrop on the background if you made sure you enabled MailDrop for that account.
You can check that by sending a test email with large attachment and check the inbox of the recipient . If it shows a preview similar to the one below, it already used MailDrop.
Let me know if you have further questions, or if this doesn't solve your problem.