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()
  • Instead of modifying the codes, you may want to give Ashley Schroder's SMTP Pro Email extension a try instead: magentocommerce.com/magento-connect/… Commented Oct 16, 2015 at 8:14
  • Are you trying to send the emails pragmatically? Or is this what appears in the logs?
    – rob3000
    Commented Oct 16, 2015 at 8:41
  • Hi, This is what appears in the logs. all other emails send fine and im using sendgrid smtp and they all show processed accept order confrmation emails which just dont send at all (or show on sendgrid activity logs) but soon as i turn the SMTP pro extension off they send again but then customers complain as they keep going to spam on the default way.
    – Michael
    Commented Oct 16, 2015 at 10:32

2 Answers 2


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.


The problem was the Bcc on the sales emails,

I changed this to seperate email and it now works

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