I'm out of options. After using the WHM transfer tool to copy my entire cpanel account to my other server for testing (did that several times without problems) there were a lot of problems, als see
https://forums.cpanel.net/threads/transfer-tool-issues.678209/
After changing back the .htaccess the site was up-and-running again. Also i did the dovecot and exim reset. Mail is sending, but incoming mail is a problem. It seems that there is a redirect or something only for incomming mail. I get this faults:
Cpanel mail
SMTP error from remote mail server after RCPT TO:[email protected]: 550-Please turn on SMTP Authentication in your mail client.\n550-cloud.tricotstoffen.nl [31.186.173.214]:50078 is not permitted to relay\n550 through this server without authentication.
Bounced mail (hotmail)
host cloud.meisjemeis.nl [31.186.173.208] SMTP error from remote mail server after RCPT TO:[email protected]: 550-Please turn on SMTP Authentication in your mail client. 550-cloud.tricotstoffen.nl [31.186.173.214]:48250 is not permitted to relay 550 through this server without authentication.
The last one contains the wrong host (cloud.meisjemeis.nl is not the correct one)
For some reason the /etc/manualmx was changed. Setting the correct value did the job