Por padrão, o dovecot executa pop , imap , pop3 e imaps nas seguintes portas :
110: pop
143: imap
995: pop3s
993: imaps
instale dovecot-pop3d e copie dovecot.socket para /etc/systemd
sudo cp /lib/systemd/system/dovecot.socket /etc/systemd/system/
sudo systemctl reenable dovecot.socket
Modifique dovecot.socket :
sudo sed -i '/:143$/s/^/#/' /etc/systemd/system/dovecot.socket
Reinicie o serviço:
sudo systemctl stop dovecot.service
sudo systemctl start dovecot.socket
sudo systemctl daemon-reload
Verifique o status:
sudo systemctl status dovecot.socket