Some mail providers implement a catch-all policy, meaning that will return positive to the RCTP TO: command. I would like to add some little addenda on top of those answers. I can confirm Joseph's and Drew's answers to use RCTP TO. In PHP I believe you can use fsockopen, fwrite and fread to perform the above steps programmatically: $smtp_server = fsockopen(".com", 25, $errno, $errstr, 30) Note too that mail servers may blacklist you if you make too many requests of them. However you may have some success at cleaning out some obviously bad email addresses by detecting invalid mail servers, or having recipient addresses rejected as above. Many mail servers will not return this information as a means to prevent against email address harvesting by spammers, so you cannot rely on this technique. I added some blank lines to make it more readable. Lines prefixed with numeric codes are responses from the SMTP server. Please tryĥ50-5.1.1 double-checking the recipient's email address for typos orĥ50-5.1.1 unnecessary spaces.
#Smtp check if email exists code
CA Business and Professions Code Section 17538.45 forbids use of this system for unsolicited electronic mail advertisements.ĥ50-5.1.1 The email account that you tried to reach does not exist. MX preference = 30, mail exchanger = .comĬ:\>telnet .com 25Ģ20 Postini ESMTP 213 y6_35_0c4 ready. MX preference = 20, mail exchanger = .com MX preference = 10, mail exchanger = .com MX preference = 40, mail exchanger = .com Here's an example of testing an email address for : You can connect to an mail server via telnet to ask whether an email address exists. I thought I'd show how you might try this in case you wanted to learn by doing it yourself. Other answers here discuss the various problems with trying to do this. This also ensures that they user entered their actual email, not a slight typo that happens to belong to somebody else. Honestly, if you're attempting to validate an address the best approach is to use a simple regex to block obviously invalid addresses, and then send an actual email with a link back to your system that will validate the email was received. This will mess up attempts to validate the address. There is also an antispam technique called greylisting, which will cause the server to reject the address initially, expecting a real SMTP server would attempt a re-delivery some time later. Other servers cannot verify the user and have to accept the message regardless. Some server will silently discard requests like this to prevent enumeration of their users. However, just because the email is not rejected, does not mean the user exists. If the user doesn't exist, you'll get a 5.1.1 DSN. You can issue a RCPT, and see if the mail is rejected. If the server responds with a 2.0.0 DSN, the user exists.
Very few servers support this command, but it is intended for exactly this. You can connect to the server, and issue a VRFY command. There are two methods you can sometimes use to determine if a recipient actually exists:
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