SMTP Checker

The SMTP Checker module allows you to enable validation of email addresses supplied by the user through any form, that uses the standard Drupal Form API, by checking the related SMTP servers.

The validation process works as follows:

• The hostname part is extracted from the email address (note: email addresses are expected to be supplied in simple format: username@hostname).
• An attempt to obtain the list of mail servers associated with the email address is made. The list is obtained by performing a lookup of the MX records defined for that hostname (note: according to the RFC 2821, when no mail exchangers are defined, the hostname itself should be used).
• For each mail server, a SMTP connection is attempted to perform a mail delivery check to the specified email address (note: no email is sent, only an attempt to do so is made).
• If a mail server responds successfully, then the email address is accepted, otherwise it is rejected with an error message.

For the administrator's convenience, failed attempts are logged to make it as easy as possible to diagnose any error that might occur during the process.

You can define which forms to apply this validation process using the settings panel for this module (admin/settings/smtp_checker).