auth-sender:the literal text auth-sender: (case sensitive) \h+any horizontal whitespace character, repeated at least once
.+any Unicode character (except for line terminators), repeated at least once
\h*any horizontal whitespace character, repeated any number of times
\R*a newline sequence, repeated any number of times
g modifier: global. Finds all matches instead of stopping after the first
u modifier: unicode. Treats the pattern and subject as UTF-16