#encoding: ASCII-8BIT
str = "praxis@tier\xC3\xA4rzte-team.ch"
p str, str.encoding
#=> "\xC2\xA92011 AACR"
#=> #<Encoding:ASCII-8BIT>

str.force_encoding('UTF-8')
p str, str.encoding
#=> "©2011 AACR"
#=> #<Encoding:UTF-8>