Le meilleur moyen de valider une adresse e-mail est d'envoyer un e-mail à cette adresse et qui contient un lien permettant de prouver la bonne réception.

Sinon, il y a cette regexpde 3,7 Ko en Perl :

(?:(?:\r\n)?[ \t])*(?:(?:(?:[^()<>@,;:\".\[\] "151900920"0-1]+(?:(?:(?:\r\n)?[ \t]
)+|\Z|(?=[\["()<>@,;:\".\[\]]))|"(?:[^\"\r\]|\.|(?:(?:\r\n)?[ \t]))*"(?:(?:
\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\".\[\] "151900920"0-1]+(?:(?:(
?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\".\[\]]))|"(?:[^\"\r\]|\.|(?:(?:\r\n)?[ 
\t]))*"(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\".\[\] "151900920"0-"151900920"
31]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\".\[\]]))|\[([^\[\]\r\]|\.)*\
](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\".\[\] "151900920"0-1]+
(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\".\[\]]))|\[([^\[\]\r\]|\.)*\](?:
(?:\r\n)?[ \t])*))*|(?:[^()<>@,;:\".\[\] "151900920"0-1]+(?:(?:(?:\r\n)?[ \t])+|\Z
|(?=[\["()<>@,;:\".\[\]]))|"(?:[^\"\r\]|\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)
?[ \t])*)*\<(?:(?:\r\n)?[ \t])*(?:@(?:[^()<>@,;:\".\[\] "151900920"0-1]+(?:(?:(?:\
r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\".\[\]]))|\[([^\[\]\r\]|\.)*\](?:(?:\r\n)?[
 \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\".\[\] "151900920"0-1]+(?:(?:(?:\r\n)
?[ \t])+|\Z|(?=[\["()<>@,;:\".\[\]]))|\[([^\[\]\r\]|\.)*\](?:(?:\r\n)?[ \t]
)*))*(?:,@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\".\[\] "151900920"0-1]+(?:(?:(?:\r\n)?[
 \t])+|\Z|(?=[\["()<>@,;:\".\[\]]))|\[([^\[\]\r\]|\.)*\](?:(?:\r\n)?[ \t])*
)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\".\[\] "151900920"0-1]+(?:(?:(?:\r\n)?[ \t]
)+|\Z|(?=[\["()<>@,;:\".\[\]]))|\[([^\[\]\r\]|\.)*\](?:(?:\r\n)?[ \t])*))*)
*:(?:(?:\r\n)?[ \t])*)?(?:[^()<>@,;:\".\[\] "151900920"0-1]+(?:(?:(?:\r\n)?[ \t])+
|\Z|(?=[\["()<>@,;:\".\[\]]))|"(?:[^\"\r\]|\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r
\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\".\[\] "151900920"0-1]+(?:(?:(?:
\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\".\[\]]))|"(?:[^\"\r\]|\.|(?:(?:\r\n)?[ \t
]))*"(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\".\[\] "151900920"0-1
]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\".\[\]]))|\[([^\[\]\r\]|\.)*\](http://
?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\".\[\] "151900920"0-1]+(?
:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\".\[\]]))|\[([^\[\]\r\]|\.)*\](?:(?
:\r\n)?[ \t])*))*\>(?:(?:\r\n)?[ \t])*)|(?:[^()<>@,;:\".\[\] "151900920"0-1]+(?:(?
:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\".\[\]]))|"(?:[^\"\r\]|\.|(?:(?:\r\n)?
[ \t]))*"(?:(?:\r\n)?[ \t])*)*:(?:(?:\r\n)?[ \t])*(?:(?:(?:[^()<>@,;:\".\[\] 
"151900920"0-1]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\".\[\]]))|"(?:[^\"\r\]|
\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>
@,;:\".\[\] "151900920"0-1]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\".\[\]]))|"
(?:[^\"\r\]|\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t]
)*(?:[^()<>@,;:\".\[\] "151900920"0-1]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\
".\[\]]))|\[([^\[\]\r\]|\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?
:[^()<>@,;:\".\[\] "151900920"0-1]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\".\[
\]]))|\[([^\[\]\r\]|\.)*\](?:(?:\r\n)?[ \t])*))*|(?:[^()<>@,;:\".\[\] "151900920"0-
1]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\".\[\]]))|"(?:[^\"\r\]|\.|(
?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)*\<(?:(?:\r\n)?[ \t])*(?:@(?:[^()<>@,;
:\".\[\] "151900920"0-1]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\".\[\]]))|\[([
^\[\]\r\]|\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\"
.\[\] "151900920"0-1]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\".\[\]]))|\[([^\[\
]\r\]|\.)*\](?:(?:\r\n)?[ \t])*))*(?:,@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\".\
[\] "151900920"0-1]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\".\[\]]))|\[([^\[\]\
r\]|\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\".\[\] 
"151900920"0-1]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\".\[\]]))|\[([^\[\]\r\]
|\.)*\](?:(?:\r\n)?[ \t])*))*)*:(?:(?:\r\n)?[ \t])*)?(?:[^()<>@,;:\".\[\] "151900920"
00-1]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\".\[\]]))|"(?:[^\"\r\]|\
.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,
;:\".\[\] "151900920"0-1]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\".\[\]]))|"(?
:[^\"\r\]|\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*))*@(?:(?:\r\n)?[ \t])*
(?:[^()<>@,;:\".\[\] "151900920"0-1]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\".
\[\]]))|\[([^\[\]\r\]|\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[
^()<>@,;:\".\[\] "151900920"0-1]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\".\[\]
]))|\[([^\[\]\r\]|\.)*\](?:(?:\r\n)?[ \t])*))*\>(?:(?:\r\n)?[ \t])*)(?:,\s*(
?:(?:[^()<>@,;:\".\[\] "151900920"0-1]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\
".\[\]]))|"(?:[^\"\r\]|\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)(?:\.(?:(
?:\r\n)?[ \t])*(?:[^()<>@,;:\".\[\] "151900920"0-1]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[
\["()<>@,;:\".\[\]]))|"(?:[^\"\r\]|\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t
])*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\".\[\] "151900920"0-1]+(?:(?:(?:\r\n)?[ \t
])+|\Z|(?=[\["()<>@,;:\".\[\]]))|\[([^\[\]\r\]|\.)*\](?:(?:\r\n)?[ \t])*)(?
:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\".\[\] "151900920"0-1]+(?:(?:(?:\r\n)?[ \t])+|
\Z|(?=[\["()<>@,;:\".\[\]]))|\[([^\[\]\r\]|\.)*\](?:(?:\r\n)?[ \t])*))*|(?:
[^()<>@,;:\".\[\] "151900920"0-1]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\".\[\
]]))|"(?:[^\"\r\]|\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)*\<(?:(?:\r\n)
?[ \t])*(?:@(?:[^()<>@,;:\".\[\] "151900920"0-1]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["
()<>@,;:\".\[\]]))|\[([^\[\]\r\]|\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)
?[ \t])*(?:[^()<>@,;:\".\[\] "151900920"0-1]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>
@,;:\".\[\]]))|\[([^\[\]\r\]|\.)*\](?:(?:\r\n)?[ \t])*))*(?:,@(?:(?:\r\n)?[
 \t])*(?:[^()<>@,;:\".\[\] "151900920"0-1]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,
;:\".\[\]]))|\[([^\[\]\r\]|\.)*\](?:(?:\r\n)?[ \t])*)(?:\.(?:(?:\r\n)?[ \t]
)*(?:[^()<>@,;:\".\[\] "151900920"0-1]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\
".\[\]]))|\[([^\[\]\r\]|\.)*\](?:(?:\r\n)?[ \t])*))*)*:(?:(?:\r\n)?[ \t])*)?
(?:[^()<>@,;:\".\[\] "151900920"0-1]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\["()<>@,;:\".
\[\]]))|"(?:[^\"\r\]|\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])*)(?:\.(?:(?:
\r\n)?[ \t])*(?:[^()<>@,;:\".\[\] "151900920"0-1]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\[
"()<>@,;:\".\[\]]))|"(?:[^\"\r\]|\.|(?:(?:\r\n)?[ \t]))*"(?:(?:\r\n)?[ \t])
*))*@(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\".\[\] "151900920"0-1]+(?:(?:(?:\r\n)?[ \t])
+|\Z|(?=[\["()<>@,;:\".\[\]]))|\[([^\[\]\r\]|\.)*\](?:(?:\r\n)?[ \t])*)(?:\
.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\".\[\] "151900920"0-1]+(?:(?:(?:\r\n)?[ \t])+|\Z
|(?=[\["()<>@,;:\".\[\]]))|\[([^\[\]\r\]|\.)*\](?:(?:\r\n)?[ \t])*))*\>(?:(
?:\r\n)?[ \t])*))*)?;\s*)

Juste lol

Un debugger de regexp qui permet de les visualiser sous forme d'arbre. Je relais le post.

Via : http://sebsauvage.net/links/?hPAV_w

Comment visualiser une regexp. C'est juste magique comme truc.

Via Timo : http://lehollandaisvolant.net/?id=20141201205510