Emails are now encrypted and no settings have been changed

[Puzzled]

iOS is up-to-date and using iPhone 6 Plus

Yesterday evening my sister-in-law and I were emailing. She replied to me from my original email. So far, so good. I replied to that email and she replied back with a subject change of "Encrypted email?" The short reply back from me was received encrypted on her iphone. I did nothing different.

I started a new email thread and everything was fine. Today, I started another email to update her on a purse I am making for her granddaughter (my great-niece). We were good for a while. I just received a reply from her that came through to me encrypted.

I am assuming they are encrypted. There is all sorts of text, equal signs, blue text, symbols, etc. Every once in a while I see a wors or two from the emails.

What is causing this? I don't know if it is my end or hers. We both had it happen with emols we sent after sending and receiving normal texts. This is very annoying.

Thank you for any assistance.

 

[933]

Maybe it's your carrier and not the phone. Try resetting your network settings. Under General, About, Reset, reset network settings. This will not wipe any data from your phone. So no worries there.
Like I said, it may be your carrier. Or hers. Have you had this issue with any other emails?? Or just ones being sent and received from the current emails?? You may want to call your carrier and see if they have been having any similar issues with anyone else if you can't get it resolved that is. Sure won't hurt. Then you may have to hit up an Apple Store or Best Buy. Until then, try some of the things being suggested like a force start of your phone, or resetting your network settings. It won't hurt anything and may help your issue. Hope you get it resolved. Have a good evening.

 

[J. A.]

In which kind of email account is this happening? Is it an Outlook account, iCloud, Gmail, Yahoo or something else?