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. The school's not happy because in their eyes I'm faulty of badly maintaining their mail server. So my question to you: do any of you guys running mail servers have similar experiences? And how do you cope with it? Cheers, Niki -- Microlinux - Solutions informatiques durables 7, place de l'église - 30730 Montpezat Site : https://www.microlinux.fr Blog : https://blog.microlinux.fr Mail : info at microlinux.fr Tél. : 04 66 63 10 32 Mob. : 06 51 80 12 12