Rainer Hasenzagl wrote:

If I switch the default charset from 'iso-8859-1' to 'UTF-8' in OTRS config (Config.pm), I cannot open any attachment (sent by an customer). (e.g. Adobe PDF- or Microsoft Word File or any other)

If I switch back to 'iso-8859-1' everything works fine. So, I suggest that it is not an DB problem --> I save all attachments in the DB (MySQL)

There seems to be a problem in otrs or Perl to distinguis between utf-8 strings and binary Data in special situations. Since utf-8 is expanding special chacters to 2 or 3 bytes, every binary data gets corrupted when this is done accidentially. In the db the data is only a blob and character set are not relevant, so everything comes out as it went in. We had a similar problem. When using utf-8 encoding we could not foreward articels with binary attachments, since the base64 encoder did not accept the Data and failed with "Wide character found". We switched to iso-8859-1 and it works. Sorry this is only an explanation, but no solution, since debugging this problem is not easy.