On Thu, Dec 10, 2020 at 02:56:17PM -0500, Viktor Dukhovni wrote: > On Thu, Dec 10, 2020 at 05:33:46AM -0800, Jon Leech wrote: > > > The only meaningful messages in the mail logs were > > > > Dec 10 00:01:58 celly postfix/smtp[21050]: warning: relayhost configuration > > problem > > Dec 10 00:01:58 celly postfix/smtp[21050]: send attr reason = unable to > > look up host mail.sonic.net: Name or service not known > > Is the "smtp" transport using "chroot" in master.cf?
It is. > > I can nslookup, dig (either A or MX records), telnet to port > > 587, etc. on mail.sonic.net, so it's not a general system DNS issue. > > Are your tests performed as "root" or as an unprivileged user? As an unprivileged user. > The chroot is always the Postfix queue directory, typically > /var/spool/postfix. And its use is specified in the "chroot" column of > the master.cf service definition. Aha, it is. NetworkManager thoughtfully erased everything from /var/spool/postfix/etc/resolv.conf shortly before these problems began, which almost certainly explains the problem. I despise NM. > A Debian update? No. But IIRC, Comcast went down for a while and I switched to tethering via my phone for data around that time, and did have to restore /etc/resolv.conf. I had no idea about the chroot resolv.conf. Thanks very much! Jon P.S. I despise NM.