Unable to connect to a Plesk server via IMAP / POP3 ports when Plesk Premium Email is installed: kolab_guam@127.0.0.1 seems to be in use by another Erlang node

Symptoms

• IMAP and POP3 connections to a Plesk server fail.

• Guam service (Plesk Premium Email's frontend for IMAP/POP3) fails to start with the following error message in  /var/log/messages (RHEL/AlmaLinux) and /var/log/syslog (Debian/Ubuntu):

  CONFIG_TEXT: epmd[491]: epmd: node name already occupied kolab_guam
  guam[1198097]: Protocol 'inet_tcp': the name kolab_guam@127.0.0.1 seems to be in use by another Erlang node

Cause

epmd service (Erlang Port Mapper Daemon) prevents Guam from starting:

# service epmd status
● epmd.service - Erlang Port Mapper Daemon
    Loaded: loaded (/lib/systemd/system/epmd.service; enabled; vendor preset: enabled)
    Active: active (running) since Fri 2025-07-25 13:45:00 +10; 1 weeks 3 days ago
    ...
    epmd[770997]: epmd: Mon Aug  4 13:45:00 2025: node name already occupied kolab_guam

By default, epmd service is stopped on Plesk for Linux servers.

Resolution

1. Connect to your Plesk server via SSH.

2. Stop and disable the epmd service:

   # systemctl disable epmd && systemctl stop epmd

   Probably, epmd.socket needs to be removed too:

   # mv /var/lib/systemd/deb-systemd-helper-enabled/sockets.target.wants/epmd.socket /root

3. Start Guam service:

   # service guam start