450 Requested mail action not taken: Invalid IP (Solution)

Hi,

I had a problem with my server that I solved and I thought I'd share the solution with you because I didn't find anything relevant information about it on google or on this forum.

For a reason that I won't discuss here, mail for an account located on server1 was being sent through the smtp of server2. Authentification was on and all.

However, the emails were rejected by a certain destination with the error : 450 Requested mail action not taken: Invalid IP

Solution was that the domain name needed and SPF record that stated that mail for that domain could originate from server2. So it was being blocked by a spam protection.

So if my client's domain is cx.com and my two servers are s1.server.com and s2.server.com, cx.com's dns entry needs

Code:

TXT "v=spf1 a:s1.server.com a:s2.server.com ?all"

But you can create an SPF record for you domain using the nice tutorial here : http://www.openspf.org/

Hope this will help someone out there

Frank