I have been using K9 for several years now without problems and am pretty happy with it. Until now I had 3 email accounts in K9 working perfectly.
Recently (3-4 weeks ago) I created a 4th email account on a new domain and added it to K9 as an IMAP account.
The problem: The “sent” folder will not show any emails I have sent through K9. It only shows emails I sent either through webmail or through Thunderbird on my desktop computer.
If I log into the webmail account and send test emails, I can see them in the sent folder in the webmail and in K9.
If I use my email program (Thunderbird) on my desktop computer to send emails, I can see them in the sent folder in Thunderbird and in K9.
On desktop or webmail: the sent folder does not contain any emails sent through K9.
I have 4 email addresses on 3 different domains.
All 3 domains are registered with and managed by gandi.net
I have K9 version 5.806
The phone is a Pixel 5 running Android 12 with all latest updates.
I have tried removing the email account with which I am having this problem and re-adding it.
I have ensured that Settings > [Account] > Sending mail > Upload sent messages is checked