Old email displaying as new notification

I’m using version 5.600 and have used K-9 for years on Android phones. I’ve noticed over there past couple weeks that it will display a notification icon at the top of the screen and when I tap it, it takes me to what I assume is a new email - only I’ve found after I’ve replied that I’ve just replied to an email that’s not new and was received days ago!

This has never happened before this so I’m assuming it’s an updated version causing the issue. I have an item listed on Craigslist so that’s why I’m finding this especially frustrating thinking I’m replying to a new message and in fact I’ve already replied to them days ago.

It’s happened several times and just happened again this morning. I don’t understand why it seems to be picking a random email that was received days ago to show as just being received. I get roughly 10 to 20 emails a day. And it’s not as if it’s the most recent unread email, because there are others that are newer that haven’t been read.

If you are using 5.6 then you aren’t using “an updated version”. [5.6 is the last “stable” version released (a year+ ago). New, beta, releases are 5.7x.] In that case, the change is likely in your back-end mail server environment. There are various things that a mail service provider (you don’t indicate which you are using) can do to mess up status flags/indicators. Additionally, if you use other clients to view/manage your mailbox they could be altering the status flags/indicators in unintended ways.

It’s an email account with my own domain name that’s hosted on Gmail. Nothing has changed that I know of with Gmail. I also use Outlook to view email on that account but it’s an older version that hasn’t been updated in a while. It just seems funny that I’ve never noticed this before and then it suddenly happened 3 times in two weeks. So far I haven’t noticed it doing it again. Thanks for the response.