I'm having some trouble with the authentication of my e-mails. gMail likes them, but Outlook and Yahoo don't. My listserver is Sender. My Sender IP is not blacklisted, and I think I have my SPF right, as v=spf1 include:sendersrv.com ?all. But Hostgator, who manages my domain, says that e-mail deliverability is improved if I include that SPF in my Zone Editor TXT for that domain. Huh? Why is that? Turns out google already has an authentication entry as a TXT record there, but Sender did not. Is that why gMail is accepting them? That is,is there more to e-mail authentication than an SPF record?