Ok, as I have a second proxmox I restarted with a clean postfix configuration, and additionally I found a post, which finaly solved all my problems. The smtp_header_checks file along with installation of postfix-pcre finally made everything work on both of my proxmox nodes, but I only tested the mailnotification for mdadm degraded raid state, and not yet on the non zfs node. General email notification for ex. after a backup works fine on the zfs node too, but I would like to ensure that zfs zed will mail me if one disk goes south.
I tested by setting one disk to faulty on the non zfs proxmox and I immediately got my email notification. One last thing I’d like to know on this topic is is the follwoing. As having had experience with mdadm, I was not afraid to set one disk to faulty. After that I knew removing it from raid and adding it back the sync will start and so it did.
Now I’d like to know, how I could test the same functionality in zfs. Being new to zfs, I thought, better ask then sorry 