Authentication-results:the literal text Authentication-results: (case sensitive) .+?any Unicode character (except for line terminators), repeated at least once
sender IPthe literal text sender IP (case sensitive) .+any Unicode character (except for line terminators), repeated at least once
\R?optionally matches a newline sequence
.+?any Unicode character (except for line terminators), repeated at least once
mailfrom=the literal text mailfrom= (case sensitive) .+?any Unicode character (except for line terminators), repeated at least once
;the literal ; (5910 / 738 / 3B16)
g modifier: global. Finds all matches instead of stopping after the first
u modifier: unicode. Treats the pattern and subject as UTF-16