I am trying to send emails using SMTP but emails are not sending using SMTP i can see in the logs i get this error
exception 'Zend_Mail_Protocol_Exception' with message 'Recipient syntax error in /lib/Zend/Mail/Protocol/Abstract.php:431
I cant see what the issue is but emails are sent using Magento Default email service but not SMTP
Here are some example Stack trace:
lib/Zend/Mail/Protocol/Smtp.php(289):Zend_Mail_Protocol_Abstract->_expect(Array, 300)
lib/Zend/Mail/Transport/Smtp.php(211): Zend_Mail_Protocol_Smtp->rcpt('')
lib/Zend/Mail/Transport/Abstract.php(348): Zend_Mail_Transport_Smtp->_sendMail()
Best Answer
Not sure if this is the same issue but I had a similar error sending magento mail using ssmtp in place of sendmail.
The problem ended up being how the bcc recipients were entered into the db. The comma separated list of emails also had a space in it, so when it was exploded based in the comma the second email actually had a space in front of it. This space was causing ssmtp to complain about the invalid email, getting rid of it fixed the problem. I was using mandrill and smtp pro before that and didn't have an issue.