I'm using an iPhone 6, running iOS 9.2.1. Recently, I experienced an issue with my iPhone email client. I hit "Reply All" on an Email A, composed my reply message, and hit "Send," but the email that was sent had some very incorrect information.

The subject line in my reply email was correct: "Re: Subject A," and the sent message included the reply text that I had composed, but the Original Message (the text that is automatically included below my signature when I reply to an email) that the email client included in the reply was NOT Email A. It was a bizarre combination of Email A and a separate message, Email B, which happened to be the most recent email I had received. To illustrate, here is what the situation looked like:

EMAIL A

From: Person A
Sent: Wednesday, June 1, 2016 12:00 PM (Date/Time A)
To: Me
Subject: Subject A

"Message Text A"

PERSON A's SIGNATURE

EMAIL B

(Completely unrelated to Email A)
From: Person B
Sent: Wednesday, June 1, 2016 12:10 PM (Date/Time B)
To: Me
Subject: Subject B

"Message Text B"

PERSON B's SIGNATURE

EMAIL C

(My email in reply to Email A—this should have only included data from Email A)
From: Me
Sent: Wednesday, June 1, 2016 12:15 PM (Date/Time C)
To: Person A
Subject: Re: Subject A

"Message Text C"

MY SIGNATURE
[Auto-populated reply header:] On Jun 1, 2016, at 12:10 PM (Date/Time B), Person A wrote:

"Message Text B"

I'm baffled by what could have caused this. As you can imagine, this caused some miscommunication, including some severe privacy concerns, and I cannot have this happen again.

It seems like when the email client was preparing Email C for me to enter my reply, it may have somehow linked Email B to Email A. Any ideas on what could have caused this, or what may have happened?