K9 Started Deleting Messages from Server


Since updating the app on my phone yesterday K9 has started deleting messages from server. This means I am no longer getting the same messages on my laptop.

My settings in the app are set as follows but it still does not work:
Sync server deletions (unticked)
Mark as read when deleted (unticked)
When I delete message (Do not delete on server, option chosen)

The ‘What’s new’ in the latest app release states: “POP3 - changed the way the list of supported authentication methods is retrieved from the server” . So I think the issue is relating to the new app settings - how do I fix?

Thank you

Welcome TurbineTerry!

It’s very unlikely that the latest update has changed how K-9 Mail behaves when it comes to deleting messages from the server.

In order to find out what is happening we need more information. What are you doing exactly? Does K-9 Mail remove messages from the server when you delete them inside the app? Do they disappear from the server once you’ve downloaded them using K-9 Mail? Do you use POP3 with both K-9 Mail and the email client on your laptop? What email provider are you using?


Thanks for the welcome. I had not made any changes at all to my account settings in K9 mail or in Outlook, the K9 mail app just started not leaving the messages on my email providers server. This means I was not getting copies in Outlook on my laptop if I had first downloaded the messages to the K9 app. This might have happened just before I did the latest update of K9, so like you say it might not have been the update that caused it.

So, as soon as the messages are downloaded to K9 app on my phone they are then deleted from the server even before/without me deleting the messages from within the K9 app. I use POP3 with K9 app and Outlook on my laptop, but I have always used POP3 and normally no issues.

I will keep trying to fix the issue, but if you have any ideas please let me know.

Thank you

p.s. my email provider is IONOS by 1and1 and I use Outlook on my laptop

IONOS changed their server software (which is why we needed to update K-9 Mail). Maybe they changed how their POP3 implementation works. Some providers decided that if clients don’t delete messages after downloading them via POP3 (like K-9 Mail), they will do it for them. There seems to be an option to disable that behavior. See the very bottom of this page: Unterschiede zwischen IMAP und POP3 - IONOS Hilfe

In general, my advice is to avoid POP3. Use IMAP instead, at least on your mobile device.

I’m also using K9, multiple pop accounts with ionos along with Outlook 2010 on one PC and Outlook 2021 on another.

Everything works as expected and email downloaded with K9 is available to other PC’s with Outlook.

My K9 settings are different…
Sync server deletions (Checked)
Mark as read when deleted (Checked)
When I delete message (Do not delete on server)

Also using ssl with the pop server.

What happens in the opposite scenario? Check for mail on PC then check in K9? Have you checked the trash in K9 to see if messages are being deleted?

A long time ago I had a situation where if a message was marked as read on ionos server (or moved), Outlook wouldn’t download the message. But if I recall this was back before ionos was 1and1.

You can log in to: mail.Ionos.com and check if the messages are on the server. Check the inbox and trash and we might get a clue what’s happening.

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