>From: Stan Hoeppner <s...@hardwarefreak.com> >To: postfix-users@postfix.org >Sent: Sunday, December 18, 2011 9:28 PM >Subject: Re: Best Practice for (not)allowing "spoofed" MAIL FROM addresses > >So to make this crystal clear, you are asking if your users should be >allowed to SUBMIT mail for RELAY through your Postfix server, with such >email having a From: header containing a domain not in your Postfix >configuration. Is this correct? I.e. roaming users who have many email >accounts and, for whatever reasons, have trouble selecting the proper >outbound relay when they send email from a particular MUA profile? > >Yes
>I guess this decision boils down to how much you trust your users. >There are a few legitimate scenarios for allowing this. One, if you're >an ISP, is customers on dynamic IP broadband who host their own mail >server and domain. As they can't send direct to MX effectively they >must relay all mail with AUTH through your server. In this case the >From: header will never match your domains. I did exactly this with >SBC/ATT/Yahoo relays for many years when I hosted my personal MX on a >dynamic IP dsl line (gasp). > >That's what I figured as thought. Some are clearly of the opinion it's heresy. >I think there are valid reasons. For those who think there are not, I presume >they've worked around non authenticated local users or programs sending mail >out that do not go through the same path as emails sent from an email client. >For example, sendmail binary. If you have not, then, you have not done what >you think. Assuming you have users you can't necessarily trust that is. Also, I've sent out mailing list for a client before from one of my servers. Since they added me as a valid sender for SPF, clearly, I should be allowed to send mail for them as if it was them since they hired us to do so (not with a purchased or robot generated list). I suppose one could simply manually add that exception in the sender map however, an argument can be made for that. Also, for me, I've always had many email addresses, many times I would funnel them all to one account. So, if I can receive email in one place, why shouldn't I be able to send email as if the email was from those places? Makes things a whole lot simpler, to me at least. Perhaps the best thing to do is simply allow anyone to send anything from their domain, and add exceptions manually as appropriate.
