Please provide details, such as the email host domain, such as gmail, outlook. What is your setting for trash on 'server settings' pane for the account?

the email host is Telfort.nl. Trash settings are not known

Is this an IMAP account or POP? Look in 'account settings', highlight the account in left side of screen and then click 'server settings' for the account and look at right side of screen to see what your settings are for that account. Do the messages still appear in the inbox or folder where you stored them? Or do they only appear when you do a search?

probleem is opgelost, bedankt voor de hulp

You're very welcome. I was glad to assist. Please mark this resolved. Thank you.