E-mail addresses are composed of the personal identifier, for example the user name, the at sign @), the host address and the top level domain( TLD). The Simple Mail Transfer Protocol( SMTP) provides that if the user identifier is unknown, it can be replaced by "postmaster". The e-mail will then be forwarded to the mail manager or webmaster. The postmaster identifier is regulated in RFC 822 for e-mails.
If, for example, the e-mail address of an employee of ITWissen is unknown, then the mail can be sent with the e-mail address email@example.com.