Absolute path is required when one has such postfix configuration
where he/she needs to specify the actual (real) path to active dovecot
config.
Without this commit applied, the dovecot is running in such way:
/nix/store/hashAAA-dovecot-ver/sbin/dovecot -F -c /nix/store/hashBBB-dovecot2.conf
and postfix can't be aware of the value of "hashBBB" via services.postfix.extraConfig = '' ... '';
(it can only be aware of "hashAAA" with ${pkgs.dovecot} parameter)
Also enable Restart on-failure.
Edit: set RestartSec to 1s
postfix 2.11 is much more humane with respect to disk writes since it uses
sockets (which do not change inodes on accesses) instead of fifos (which do).
Using pkgs.lib on the spine of module evaluation is problematic
because the pkgs argument depends on the result of module
evaluation. To prevent an infinite recursion, pkgs and some of the
modules are evaluated twice, which is inefficient. Using ‘with lib’
prevents this problem.
That is, you can say
security.pam.services.sshd = { options... };
instead of
security.pam.services = [ { name = "sshd"; options... } ];
making it easier to override PAM settings from other modules.
