In the last weeks, I noticed that spam activity was back, including against centos.org infra. One of the most used technique was for centos.org (while some of the Infra team members had that on their personal SMTP servers).
While SPF itself is "just" a TXT dns record in your zone, you have to think twice before implementing it. And publishing yourself such a policy doesn't mean that your SMTP servers are checking SPF either. There are PROS and CONS to SPF so read first multiple sources/articles to understand how it will impact your server/domain when sending/receiving :
sending
The first thing to consider is how people having an alias can send send their mails : either behind their known MX borders (and included in your SPF) or through alternate SMTP servers relaying (after of course) through servers listed in your SPF.
One thing to know with SPF is that it breaks but it's not how you will setup your SPF record, but how originator domain does it : For example if you have [email protected] sending to [email protected] itself being an alias to [email protected], that will break, as MX for domain.com will see that a mail for domain.com was 'sent' from otherdomain.com and not from an IP listed in their SPF. There are workaround for this though, aka remailing and 2.10, there is nothing by default that let you verify SPF : as stated on : lightweight, easy , written in python. The needed packages are already available in Epel, but we also . Once installed, with Postfix, you'll start (based on your .conf settings) blocking mail that arrives to your SMTP servers, but from IP/servers not listed in the originator domain SPF policy (if any).
If you have issues with our SPF current policy on centos.org, feel free to reach us in #centos-devel on irc.freenode.net to discuss it.
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