# apt install sendmail
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following additional packages will be installed:
  procmail sendmail-base sendmail-bin sendmail-cf sensible-mda
Suggested packages:
  sendmail-doc rmail logcheck sasl2-bin
The following NEW packages will be installed:
  procmail sendmail sendmail-base sendmail-bin sendmail-cf sensible-mda
0 upgraded, 6 newly installed, 0 to remove and 2 not upgraded.
Need to get 1,919 kB of archives.
After this operation, 4,213 kB of additional disk space will be used.
Do you want to continue? [Y/n]
Get:1 http://cdn-fastly.deb.debian.org/debian sid/main amd64 sendmail-base all 8.15.2-11 [343 kB]
Get:2 http://cdn-fastly.deb.debian.org/debian sid/main amd64 sendmail-cf all 8.15.2-11 [291 kB]
Get:3 http://cdn-fastly.deb.debian.org/debian sid/main amd64 sendmail-bin amd64 8.15.2-11 [695 kB]
Get:4 http://cdn-fastly.deb.debian.org/debian sid/main amd64 procmail amd64 3.22-26 [142 kB]
Get:5 http://cdn-fastly.deb.debian.org/debian sid/main amd64 sensible-mda amd64 8.15.2-11 [225 kB]
Get:6 http://cdn-fastly.deb.debian.org/debian sid/main amd64 sendmail all 8.15.2-11 [223 kB]
Fetched 1,919 kB in 3s (641 kB/s)
Selecting previously unselected package sendmail-base.
(Reading database ... 1536936 files and directories currently installed.)
Preparing to unpack .../0-sendmail-base_8.15.2-11_all.deb ...
Unpacking sendmail-base (8.15.2-11) ...
Selecting previously unselected package sendmail-cf.
Preparing to unpack .../1-sendmail-cf_8.15.2-11_all.deb ...
Unpacking sendmail-cf (8.15.2-11) ...
Selecting previously unselected package sendmail-bin.
Preparing to unpack .../2-sendmail-bin_8.15.2-11_amd64.deb ...
Unpacking sendmail-bin (8.15.2-11) ...
Selecting previously unselected package procmail.
Preparing to unpack .../3-procmail_3.22-26_amd64.deb ...
Unpacking procmail (3.22-26) ...
Selecting previously unselected package sensible-mda.
Preparing to unpack .../4-sensible-mda_8.15.2-11_amd64.deb ...
Unpacking sensible-mda (8.15.2-11) ...
Selecting previously unselected package sendmail.
Preparing to unpack .../5-sendmail_8.15.2-11_all.deb ...
Unpacking sendmail (8.15.2-11) ...
Setting up procmail (3.22-26) ...
Setting up sendmail-base (8.15.2-11) ...
adduser: Warning: The home directory `/var/lib/sendmail' does not belong to the user you are currently creating.
update-inetd: warning: cannot add service, /etc/inetd.conf does not exist
update-inetd: warning: cannot add service, /etc/inetd.conf does not exist
update-inetd: warning: cannot add service, /etc/inetd.conf does not exist
update-inetd: error: --group is only relevant with --add
dpkg: error processing package sendmail-base (--configure):
 installed sendmail-base package post-installation script subprocess returned error exit status 255
Processing triggers for systemd (239-7) ...
Setting up sendmail-cf (8.15.2-11) ...
Processing triggers for man-db (2.8.4-2) ...
dpkg: dependency problems prevent configuration of sendmail-bin:
 sendmail-bin depends on sendmail-base (= 8.15.2-11); however:
  Package sendmail-base is not configured yet.

dpkg: error processing package sendmail-bin (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of sensible-mda:
 sensible-mda depends on sendmail-bin | mail-transport-agent; however:
  Package sendmail-bin is not configured yet.
  Package mail-transport-agent is not installed.
  Package sendmail-bin which provides mail-transport-agent is not configured yet.

dpkg: error processing package sensible-mda (--configure):
 dependency problems - leaving unconfigured
dpkg: dependency problems prevent configuration of sendmail:
 sendmail depends on sendmail-base; however:
  Package sendmail-base is not configured yet.
 sendmail depends on sendmail-bin; however:
  Package sendmail-bin is not configured yet.
 sendmail depends on sensible-mda; however:
  Package sensible-mda is not configured yet.

dpkg: error processing package sendmail (--configure):
 dependency problems - leaving unconfigured
Errors were encountered while processing:
 sendmail-base
 sendmail-bin
 sensible-mda
 sendmail
E: Sub-process /usr/bin/dpkg returned an error code (1)