لطفا منتظر باشید ...
6.19. Matching a Valid Mail Address
6.19.1. Problem
You want to find a pattern to
verify the validity of a supplied mail address.
6.19.2. Solution
Because you cannot do real-time validation of deliverable mail
addresses, no single, succinct pattern will solve this problem. You
must pick from several available compromise approaches.
6.19.3. Discussion
Our best advice for verifying a person''s mail address is to have them
enter their address twice, just as you would when changing a
password. This usually weeds out typos. If both entries match, send
mail to that address with a personal message such as:
Dear someuser@host.com,
Please confirm the mail address you gave us on Sun Jun 29
10:29:01 MDT 2003 by replying to this message. Include the
string "Rumpelstiltskin" in that reply, but spelled in reverse;
that is, start with "Nik...". Once this is done, your confirmed
address will be entered into our records.
If you get back a message where they''ve followed your directions, you
can be reasonably assured that it''s real. A related strategy that''s
less open to forgery is to give them a personal identification number
(PIN). Record the address and PIN (preferably a random one) for later
processing. In the mail you send, ask them to include the PIN in
their reply. In case your email bounces, or the message is included
via a vacation script, ask them to mail back the PIN slightly
altered, such as with the characters reversed, one added or
subtracted to each digit, etc.Most common patterns used for address verification or validation fail
in various and sometimes subtle ways. For example, the address
this&that@somewhere.com is valid and quite
possibly deliverable, but most patterns that allegedly match valid
mail addresses fail to let that one pass.
1 while $addr =~ s/\([^( )]*\)//g;
You could use the 6598-byte pattern given on the
last page of the first edition of Mastering Regular
Expressions to test for RFC conformance, but even that
monster isn''t perfect, for three reasons.First, not all RFC-valid addresses are deliverable. For example,
foo@foo.foo.foo.foo is valid in form, but in
practice is not deliverable. Some people try to do DNS lookups for MX
records, even trying to connect to the host handling that address''s
mail to check if it''s valid at that site. This is a poor approach
because most sites can''t do a direct connect to any other site, and
even if they could, mail-receiving sites increasingly either ignore
the SMTP VRFY command or fib about its answer.Second, some RFC-invalid addresses, in practice, are perfectly
deliverable. For example, a lone postmaster is
almost certainly deliverable, but doesn''t pass RFC 822 muster: it
doesn''t have an @ in it.Finally and most importantly, just because the address happens to be
valid and deliverable doesn''t mean that it''s the right one.
president@whitehouse.gov, for example, is valid by
the RFC and deliverable. But it''s unlikely in the extreme that that
would be the mail address of the person submitting information to
your CGI script.The
Email::Valid CPAN module makes a valiant (albeit provably imperfect)
attempt at doing this correctly. It jumps through many hoops,
including the RFC 822 regular expression from Mastering
Regular Expressions, DNS MX record lookup, and stop lists
for naughty words and famous people. But this is still a weak
approach. The approach suggested at the beginning of the Discussion
is easier to implement and less prone to error.
6.19.4. See Also
The "Matching an Email Address" section of Chapter 7 of the first
edition Mastering Regular Expressions; Recipe 18.16
