I have a domain on my host which I've added to Gmail. It has the following SPF record,
"v=spf1 a ~all"
All emails that I send from Gmail are correctly verified and have the following header,
spf=pass (google.com: domain of email@example.com designates 123.456.789.10 as permitted sender).
I'm wondering how did that happen since I haven't added any Gmail IP to the record? Is it not necessary?
EDIT: The IP 123.456.789.10 in the message source is of my host. I always thought that since I've added the domain to gmail, it is gmail that sends the email. How does this actually work?