iOS 7: Mail can switch your From address if you’re emailing a coworker, team member

This is probably best described through anecdote: my default send-from address in Mail on iOS is my account. But if I type the first couple letters of an AgileBits colleague in the To field, then select the suggested contact from my address book with an address, Mail switches my From address to my Agilebits account.
I tinkered with this a bit to try and figure out what logic Mail is using, but I can’t pin it down. For example, I set my default account to iCloud, then tried drafting messages to some of the aliases I use for things like contact forms. Mail does not automatically switch my From address to my account, and I think it’s because none of those aliases are tied to a contact in my device.

If anyone has a better explanation of how this works, I’m all ears.

[via Rune Madsen]