Guess what does this validate:
(?:(?:\r\n)?[ \t])*(?:(?:(?:[^()@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t]
)+|\Z|(?=[\["()@,;:\\".\[\]]))|”(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*”(?:(?:
\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()@,;:\\".\[\] \000-\031]+(?:(?:(
?:\r\n)?[ \t])+|\Z|(?=[\["()@,;:\\".\[\]]))|”(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[
\t]))*”(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t])*(?:[^()@,;:\\".\[\] \000-\0
31]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\
](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()@,;:\\".\[\] \000-\031]+
(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()@,;:\\".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:
(?:\r\n)?[ \t])*))*|(?:[^()@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z
|(?=[\["()@,;:\\".\[\]]))|”(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*”(?:(?:\r\n)
?[ \t])*)*\(?:(?:\r\n)?[ \t])*)|(?:[^()@,;:\\".\[\] \000-\031]+(?:(?
:(?:\r\n)?[ \t])+|\Z|(?=[\["()@,;:\\".\[\]]))|”(?:[^\"\r\\]|\\.|(?:(?:\r\n)?
[ \t]))*”(?:(?:\r\n)?[ \t])*)*:(?:(?:\r\n)?[ \t])*(?:(?:(?:[^()@,;:\\".\[\]
\000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()@,;:\\".\[\]]))|”(?:[^\"\r\\]|
\\.|(?:(?:\r\n)?[ \t]))*”(?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()
@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()@,;:\\".\[\]]))|”
(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ \t]))*”(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t]
)*(?:[^()@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()@,;:\\
".\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?
:[^()@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()@,;:\\".\[
\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\r\n)?[ \t])*))*|(?:[^()@,;:\\".\[\] \000-
\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()@,;:\\".\[\]]))|”(?:[^\"\r\\]|\\.|(
?:(?:\r\n)?[ \t]))*”(?:(?:\r\n)?[ \t])*)*\(?:(?:\r\n)?[ \t])*)(?:,\s*(
?:(?:[^()@,;:\\".\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()@,;:\\
".\[\]]))|”(?:[^\"\r\\]|\\.|(?:(?:\r\n)?[ [...]