Is this setup considered email spoofing?

Question

If I have an email server A (domainA.com) and another email server B (domainB.com), is it considered spoofing if I choose to send an email from server A with the return/sender address something@domainB.com?

How will this affect spam filters?

I am wondering because I use a third party vendor to send emails on my behalf and it is easiest if they do it from their own servers rather than mine. If this is bad practice then how do you suggest I accomplish this goal?

Answer 1

There should not be any problems as long as you follow a few Guidelines:

• implement SPF, and define the IP address of server B in the list of allowed IP to send emails for domain A.
  this will help you with all of the Organizations that are enforcing SPF.
• Make sure that Server B has a PTR record and if server B also receives mail from domain A, make sure to have the correct MX records on the DNS server.

Of course all of that would not help if the contents of the email all malformed, contains suspicious headers or bad words.

Answer 2

I send email through several ISPs, always using the same from address. Sometimes you have to ask the ISP to allow mail from a domain that isn't registered with them, sometimes not.

Other than that, I've not encountered any problems.

Answer 3

If the SPF header for domainB.com explicitly permits mail to be sent from server A, then there are no problems. You should have an SPF header anyway, to prevent unauthorised people sending email on your behalf. For information on configuring SPF, see http://www.openspf.org/Introduction

Answer 4

Route your emails through the provider and then take this Email Server Test. It will flag things that can make your email be considered as SPAM.