[Mailman-Users] 'list not found' after kernel upgrade

[David Josephson]

We have been running Mailman 2.1.18-1 for a long time, on a Centos 7 
system with sendmail. We do a yum update every few months. Coincident 
with the last one, which included a kernel update to 3.10, mailman 
stopped working, posts are bounced back with this message:

     ----- The following addresses had permanent fatal errors -----
"|/etc/smrsh/mailman post ampex"
      (reason: 1)
      (expanded from: <ampex at lena.recordist.com>)

     ----- Transcript of session follows -----
post script, list not found: ampex
554 5.3.0 unknown mailer error 1

Mailman log says the same thing,

Aug 18 05:46:09 2016 post(1452): post script, list not found: ampex

Maillog says

Aug 19 13:29:43 lena sendmail[10931]: u7JKTgkW010930: 
to="|/etc/smrsh/mailman post ampex", ctladdr=<ampex at recordist.com> 
(8/0), delay=00:00:00, xdelay=00:00:00, mailer=prog, pri=32792, 
dsn=5.3.0, stat=unknown mailer error 1

Qrunner is running, sendmail is working normally. SELinux is disabled. 
There is nothing but default in mm_cfg.py, which hasn't changed since 2015.

The yum update can't be rolled back because of the kernel upgrade.

I noticed that the symbolic link in /etc/smrsh was touched about the 
same time as the update.

Clues?