Question

Exact Duplicate: Using a regular expression to validate an email address

What are valid email address characters and patterns and how would you write a regular expression which matches it?

Answer 1

Here you go:

(?:(?:\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])*(?:[^()<>@,;:\\'.\[\] \000-\031]+(?:(?:(?:\r\n) ?[ \t])+|\Z|(?=[\['()<>@,;:\\'.\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\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])*))*) *:(?:(?:\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])*))*\>(?:(?:\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])*(?:@(?:[^()<>@,; :\\'.\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\['()<>@,;:\\'.\[\]]))|\[([ ^\[\]\r\\]|\\.)*\](?:(?:\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])*)(?:\.(?:(?:\r\n)?[ \t])*(?:[^()<>@,;:\\'.\[\]  \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\['()<>@,;:\\'.\[\]]))|\[([^\[\]\r\\] |\\.)*\](?:(?:\r\n)?[ \t])*))*)*:(?:(?:\r\n)?[ \t])*)?(?:[^()<>@,;:\\'.\[\] \0 00-\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])*))*\>(?:(?:\r\n)?[ \t])*)(?:,\s*( ?:(?:[^()<>@,;:\\'.\[\] \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])*(?:@(?:[^()<>@,;:\\'.\[\] \000-\031]+(?:(?:(?:\r\n)?[ \t])+|\Z|(?=[\[' ()<>@,;:\\'.\[\]]))|\[([^\[\]\r\\]|\\.)*\](?:(?:\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])*)(?:\.(?:(?:\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]))*'(?:(?:\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])*))*\>(?:( ?:\r\n)?[ \t])*))*)?;\s*) 

No, I’m not joking. http://www.ex-parrot.com/~pdw/Mail-RFC822-Address.html