Question : 554 This server requires PTR for unauthenticated connections.

Hi,

When trying to send email to a few domain, I get this error: 554 This server requires PTR for unauthenticated connections.

I read that it is all about the PTR / Reverse DNS record.
The thing I don't understand is that what if I have 10 domains installed on 1 IP. How can this one IP reverse DNS to all 10 domains?

Thanks

Answer : 554 This server requires PTR for unauthenticated connections.

You can do that if you wish. I have seen many sites allow the user to use their own domain - as DNS lets you have as many hosts pointing to an IP address as you like.

However for outbound traffic, the server can only have one identity. Make sure that it resolves correctly - so the forward and reverse DNS both match the SMTP banner.
That will deal with the PTR error you are receiving.
On the MX records it depends on how strict the receiving site is being. You cannot control that, so all you can do is limit the risk.

If you haven't already, make suer that you have SPF records for all domains that allows your server's real name to be able to send email for that domain.

Simon.