alps frequently fails to start (e.g. during a system activation script)
since either its configured imap or smtp servers are not reachable
yet (i.e. their process has not yet opened the corresponding port).
This should hopefully fix that behaviour:
- also set BindsTo, telling systemd to only start alps once the
required units have entered "active" state (not just after it has
started them)
- also require postfix to be present, since that provides smtp
stuebinm
319e5894e0