On one of our machines the original Sysadmin had setup Sendmail, but on all our other machines the default version installed by Ubuntu is Postfix. Rather than having to maintain and troubleshoot several type of systems, I wanted the sendmail one to be changed to match our Postfix systems.
The advice at this forum post which said to simply apt-get install postfix and it would automatically remove Sendmail. Which it did. Goes into the postfix screen and I set it up as per usual. However, when testing it out from the command line by trying to send a logwatch report, I get this error:
postdrop: warning: unable to look up public/pickup: No such file or directory
Thanks to this article at databasically.com I found out that Ubuntu wasn’t removing sendmail completely, in fact it wasn’t stopping the sendmail process! Here’s the solution that was posted:
mkfifo /var/spool/postfix/public/pickup ps aux | grep mail kill [insert process number] sudo /etc/init.d/postfix restart