Outgoing e-mails show weird signs in the subject line like: “=?utf-8?b?W0F1Y3Rpb25zXSBOZXcgYmlkIG9uIFBpYWdnaW8gUDE4MCBBdmFudGk=?=”

There is an option in the settings “BYPASS UTF8 EMAIL” which you can change (somewhere at the bottom of the auction settings tab) that will fix this.