Hi, This is not a bug in MIME::tools.
The OP misunderstands how Perl works. He typed UTF-8 source code in and is double encoding it. Here's a test program: #=================================================================== use MIME::Words; use Encode; my $sample = "Re: Bildungsurlaub für CCC-Fahrt? [THD#1424195]"; my $utf8 = Encode::encode('UTF-8', $sample); my $out = MIME::Words::encode_mimewords($utf8, Charset => 'UTF-8'); print "Out: $out\n"; #=================================================================== If I run: perl test-utf8.pl Output is: Out: Re: Bildungsurlaub =?UTF-8?Q?f=C3=83=C2=BCr=20?=CCC-Fahrt? [THD#1424195] But that's because the word "für" is *already* UTF-8. If I tell Perl to convert UTF-8 in the source code to native Perl Unicode, the result is very different: perl -Mutf8 test-utf8.pl Output is: Out: Re: Bildungsurlaub =?UTF-8?Q?f=C3=BCr=20?=CCC-Fahrt? [THD#1424195] The OP should read "perldoc utf8" and should also not use UTF-8 directly as Perl source code; use \x{FC} rather than ü, etc. Regards, Dianne.