I am setting up Postfix mail server. What I want to know is that, what the popular mail server's like yahoo, gmail, AOL, Microsoft Outlook server etc. use for sender identification of e-mails.

e.g: Which one use SPF or DKIM or SenderId etc.

Any listing enumerating about these properties would be highly useful.

Thanks in advance


  • FYI, Outlook is a client, not a server. – John Gardeniers Oct 19 '09 at 11:30

Yahoo! uses DKIM. Google uses both SPF and DKIM. Microsoft/Hotmail use SenderID, which is a slight variation of SPF.

Outblaze (Now IBM iNotes) uses neither.

What is your actual goal though?

  • My actual goal is to create a setup of a postfix installation that uses best of all available mail server's in terms of standards. – Ashish Sharma Oct 19 '09 at 11:10
  • You're not limited to using only one. I've correct SPF records and dkim-milter running on my postfix server. – user17642 Oct 24 '09 at 5:18
  • There is no "best". Why are you doing this in the first place? – Devdas Dec 13 '09 at 19:45

Yahoo! is using Domainkeys which is different than DKIM.


Google is using SPF. Some headers from email:

Received-SPF: pass (google.com: domain of EMAILADDRESS designates IPNUMBER as permitted sender) client-ip=IPNUMBER;
Authentication-Results: mx.google.com; spf=pass (google.com: domain of EMAILADDRESS t designates IPNUMBER as permitted sender) smtp.mail=EMAILADDRESS 

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