I am using Debian 4.0 (Etch), squirrelmail 1.4.9a-2, PHP 4.4.4-8+etch4, MTA is Postfix 2.3.8-2+ba
I find when I try to send a mail to an email address such email@example.com (0 is zero). After I click "Send", an error come out:
Server replied: 554 5.5.1 Error: no valid recipients
Please take a look of the attached file which is the log capture from the server.
There is no "RCPT TO" header sent to SMTP server for firstname.lastname@example.org (in the log it is email@example.com I will attach another log which is send an email to firstname.lastname@example.org (in the log it is email@example.com). In this test, it does have "RCPT TO".