Dear List,
Gmail has made some changes so with emails that are not sent from the domain of the email address (eg: an email from donald@duck.com sent by an SMTP server smtp.alligator.com) I get warnings such as "This message may not have been sent by: donald@duck.com", and/or the sender is displayed as " donald@duck.com via alligator.com". I've made some research and all this is because of increasing protection against email spoofing. The solution is to add a so-called SPF (Sender Policy Framework) record to your DNS records. (More info: http://www.openspf.org/) Some ISPs like Godaddy support it with their DNS editor, some others need to add a TXT record manually (in my case something like this: "v=spf1 mx mx: smtp.myisp.net include:smtp.gmail.com include:myotherisp.net -all").
Hope this helps some of you.
Andras