The Sender Policy Framework (SPF) is a method of fighting spam. As more time passes, this protocol will be used as one of the standard methods of fighting spam on the Internet. An SPF record is a TXT record that is part of a domain's DNS zone file. The TXT record specifies a list of authorized host names/IP addresses where mail can originate from for a given domain name. Once this entry is placed within the DNS zone, no further configuration is necessary to take advantage of servers that incorporate SPF checking into their anti-spam systems. This SPF record is added the same way as a regular A, MX, or CNAME record.
• To generate an appropriate SPF record for your domain visit this link: http://www.spfwizard.com
• To validate an added SPF record visit this link: http://www.kitterman.com/spf/validate.html
Adding an SPF record to your zone file is the best way to stop spammers from using this technique with your domain. An SPF record will eliminate a high proportion of the bouncebacks you've been getting, because other mail providers will reject the email immediately without sending a bounceback to the (spoofed) reply-to address. While the SPF record is not 100% effective, because not all mail providers check for it, you should notice a drastic decrease in the amount of bouncebacks you receive.