On Thu, 8 Oct 2020 at 17:50, Nicolas Kovacs <info at microlinux.fr> wrote: > Hi, > > This is probably a bit OT, but here goes. > > I've been running our local school's mail server since 2013, with mail > addresses for school staff and some teachers. The server is running CentOS > 7 > with Postfix and Dovecot, and it's a nice no-bullshit configuration with > SPF, > DKIM and DMARC. > > The school sends quite a lot of email out to parents, and sometimes, mail > gets > rejected: > > --8<-------------------------------------------------------- > <xxxxxxxx at orange.fr>: host smtp-in.orange.fr[193.252.22.65] said: 550 > 5.2.0 > Mail rejete. Mail rejected. ofr_506 [506] (in reply to end of DATA > command) > > <yyyyyyyy at wanadoo.fr>: host smtp-in.orange.fr[193.252.22.65] said: 550 > 5.2.0 > Mail rejete. Mail rejected. ofr_506 [506] (in reply to end of DATA > command) > --8<-------------------------------------------------------- > > This happens randomly with the usual suspects among crappy mail providers > like > Orange, Hotmail/Live, Yahoo and the rest. > > So wanadoo and orange seem to send a ofr_506 because the scanned mail was found to be SPAM. This is independent of DKIM, SPF, DMARC but from them scanning the email in the DATA and saying nope. Usually that is because too many people complained about a set of email and the weight of email with that content is getting blocked. I don't know if the school moving to another provider will fix that as this isn't because of the IP it was sent from (they block before the DATA is sent in that case). [My guess is that someone wants to move to something else and is using this as the Casus Belli to do so. ] I don't really have a suggestion or solution to either problem.. > -- Stephen J Smoogen.