Sending e-mail from Proxmox to guest fails, Connection timed out

[Tapio Lehtonen]

This used to work, but stopped working on Thursday morning when I rebooted host (and guests).
Now mails stay in mailq. I can send e-mails to GMail, though. So port 25 is open to Internet but maybe it is closed between host and guest?
I can ping guests.
Telnet to guest port 25 outputs "Trying ..." and nothing happens.
When I examine Firewall for guest in Proxmox GUI log has no content and Options shows Firewall No.
For host Firewall shows Yes, log has only "0 5 - 13/Mar/2021:00:00:02 +0200 starting pvefw logger".

# pveversion -v
proxmox-ve: 6.3-1 (running kernel: 5.4.101-1-pve)
pve-manager: 6.3-4 (running version: 6.3-4/0a38c56f)
pve-kernel-5.4: 6.3-6
pve-kernel-helper: 6.3-6
pve-kernel-5.4.101-1-pve: 5.4.101-1
pve-kernel-5.4.98-1-pve: 5.4.98-1
pve-kernel-5.4.73-1-pve: 5.4.73-1
ceph-fuse: 12.2.11+dfsg1-2.1+b1
corosync: 3.1.0-pve1
criu: 3.11-3
glusterfs-client: 5.5-3
ifupdown: 0.8.35+pve1
ksm-control-daemon: 1.3-1
libjs-extjs: 6.0.1-10
libknet1: 1.20-pve1
libproxmox-acme-perl: 1.0.7
libproxmox-backup-qemu0: 1.0.3-1
libpve-access-control: 6.1-3
libpve-apiclient-perl: 3.1-3
libpve-common-perl: 6.3-4
libpve-guest-common-perl: 3.1-5
libpve-http-server-perl: 3.1-1
libpve-storage-perl: 6.3-7
libqb0: 1.0.5-1
libspice-server1: 0.14.2-4~pve6+1
lvm2: 2.03.02-pve4
lxc-pve: 4.0.6-2
lxcfs: 4.0.6-pve1
novnc-pve: 1.1.0-1
proxmox-backup-client: 1.0.8-1
proxmox-mini-journalreader: 1.1-1
proxmox-widget-toolkit: 2.4-5
pve-cluster: 6.2-1
pve-container: 3.3-4
pve-docs: 6.3-1
pve-edk2-firmware: 2.20200531-1
pve-firewall: 4.1-3
pve-firmware: 3.2-2
pve-ha-manager: 3.1-1
pve-i18n: 2.2-2
pve-qemu-kvm: 5.2.0-2
pve-xtermjs: 4.7.0-3
qemu-server: 6.3-5
smartmontools: 7.1-pve2
spiceterm: 3.1-1
vncterm: 1.6-2
zfsutils-linux: 2.0.3-pve2

 

[Tapio Lehtonen]

On host

# pve-firewall status
Status: disabled/running

What does that mean? Is firewall disabled or running? It can not be both, or can it?
I have fail2ban running on host, it has banned lots of IP-numbers so iptables is active on host. I have not done any firewall setup in Proxmox, as far as I know.
On another guest running on this Proxmox host I can telnet to port 25 and get the ESMTP Postfix answer back. So port 25 is open on my guest host running postfix.