Hi LuKreme, > On Mar 4, 2018, at 8:44 AM, LuKreme <krem...@kreme.com> wrote: > > Isn't ETRN a good thing? What's the benefit from disabling it? > -- > My main job is trying to come up with new and innovative and effective ways > to reject even more mail. I'm up to about 97% now. >
It’s a good thing in that it is an improvement over the original TURN verb with some security as opposed to no security. RFC 1985 (ETRN) makes two use cases for this: ** Startup conditions ** “..mail nodes that have transient connections to their service providers” The last point is referring to when someone had a gateway SMTP server that used to periodically dial up an ISP and exchange e-mail with it, server to server. That was common in the 90’s (which is when the RFC was submitted), but you’d be pretty hard pressed to find that now. Postfix supports fast ETRN [1], which has performance optimizations over what other implementations provide, but you have to explicitly configure it to use it. From my original e-mail I learned from the list how to squelch the advertisement on EHLO and ensure that it was not configured, either. Sources: [1] http://www.postfix.org/ETRN_README.html
