Regular Expression for delimited email address

Question

i am looking for a regular express to validate a list of email addresses like the following

test1@abd.com;test.test@abc.com;test3@test.com

and

Answer 1

“You call that a knife???” —Crocodile Dundee

Actually, all those are very poor patterns for matching a mail address. To strictly validate an RFC 5322 mail address with zero false negatives and zero false positives, you need this precise pattern:

  (?x)

  (?(DEFINE)

     (?
         (?&mailbox) | (?&group))
     (?         (?&name_addr) | (?&addr_spec))
     (?       (?&display_name)? (?&angle_addr))
     (?      (?&CFWS)? < (?&addr_spec) > (?&CFWS)?)
     (?           (?&display_name) : (?:(?&mailbox_list) | (?&CFWS))? ; (?&CFWS)?)
     (?    (?&phrase))
     (?    (?&mailbox) (?: , (?&mailbox))*)

     (?       (?&local_part) \@ (?&domain))
     (?      (?&dot_atom) | (?"ed_string))
     (?          (?&dot_atom) | (?&domain_literal))
     (?  (?&CFWS)? \[ (?: (?&FWS)? (?&dcontent))* (?&FWS)?
                                   \] (?&CFWS)?)
     (?        (?&dtext) | (?"ed_pair))
     (?           (?&NO_WS_CTL) | [\x21-\x5a\x5e-\x7e])

     (?           (?&ALPHA) | (?&DIGIT) | [!#\$%&'*+-/=?^_`{|}~])
     (?            (?&CFWS)? (?&atext)+ (?&CFWS)?)
     (?        (?&CFWS)? (?&dot_atom_text) (?&CFWS)?)
     (?   (?&atext)+ (?: \. (?&atext)+)*)

     (?            [\x01-\x09\x0b\x0c\x0e-\x7f])
     (?     \\ (?&text))

     (?           (?&NO_WS_CTL) | [\x21\x23-\x5b\x5d-\x7e])
     (?        (?&qtext) | (?"ed_pair))
     (?   (?&CFWS)? (?&DQUOTE) (?:(?&FWS)? (?&qcontent))*
                          (?&FWS)? (?&DQUOTE) (?&CFWS)?)

     (?            (?&atom) | (?"ed_string))
     (?          (?&word)+)

     # Folding white space
     (?             (?: (?&WSP)* (?&CRLF))? (?&WSP)+)
     (?           (?&NO_WS_CTL) | [\x21-\x27\x2a-\x5b\x5d-\x7e])
     (?        (?&ctext) | (?"ed_pair) | (?&comment))
     (?         \( (?: (?&FWS)? (?&ccontent))* (?&FWS)? \) )
     (?            (?: (?&FWS)? (?&comment))*
                         (?: (?:(?&FWS)? (?&comment)) | (?&FWS)))

     # No whitespace control
     (?       [\x01-\x08\x0b\x0c\x0e-\x1f\x7f])

     (?           [A-Za-z])
     (?           [0-9])
     (?            \x0d \x0a)
     (?          ")
     (?             [\x20\x09])
   )

   (?&address)  # finally, match a mail address

I discuss this in more detail in this answer.

That needs a Perl Compatible Regular Expression (PCRE) library, or Perl itself, to work properly. I cannot guarantee that perl incompatible pattern engines will correctly handle the recursion.