Please help to set up SPF records for "mydomain.com".
I am sending mail from:
1) server where website "mydomain.com" is hosted. IP address 18.104.22.168 2) from Gmail servers (MX records) 3) I am also using third party SMTP server "mail.otherserver.com", IP address 22.214.171.124 (reverse record for 126.96.36.199 is mail.otherserver.com)
I don't want to allow sending mail from any other servers.
"v=spf1 a mx a:mail.otherdomain.com include:mail.otherserver.com ~all"
Google's version is the following (for MX servers):
v=spf1 include:_spf.google.com ~all
I don't understand the following things: 1. Why Open SPF uses just "mx" for MX records but Hotmail lists all MX records. The same with A record where is used "a" and IP4. 3. Why Google tells to use "_spf.google.com" - none of MX records contain "google.com". 4. Why Hotmail's version is "a:mail.otherserver.com" but Open SPF uses "include:mail.otherserver.com". Where is the difference between "a" and "include".