#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "(\[\[outlook:)([0-9A-Z]*)(\]\[)(.*)(\]\])"
Local $sString = "[[outlook:000000003730C053465F314590D066368CF3097B0700AAF83E03F96EDC42918E044642DEDDB3000013E2000E0000AAF83E03F96EDC42918E044642DEDDB3000013E2EFD30000][MESSAGE: RE: Subject of the Message (Sendername Senderfirstname) 2014-08-05 19:48]]" & @CRLF & _
"" & @CRLF & _
"[[http:000000003730C053465F314590D066368CF3097B0700AAF83E03F96EDC42918E044642DEDDB3000013E2000E0000AAF83E03F96EDC42918E044642DEDDB3000013E2EFD30000][MESSAGE: RE: Subject of the Message (Sendername Senderfirstname) 2014-08-05 19:48]]"
Local $sSubst = "[[path\\outlook\\\2\.msg\3\4\5"
Local $sResult = StringRegExpReplace($sString, $sRegex, $sSubst)
MsgBox($MB_SYSTEMMODAL, "Result", $sResult)
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for AutoIt, please visit: https://www.autoitscript.com/autoit3/docs/functions/StringRegExp.htm