Mailenable server is used as default mail server. It is not possible to login to mail account created under this mail server.
Opening account properties in MailEnable we see that password is empty and the error window displayed:
Failed to get password entry from authentication configuration store...
MailEnable configuration files are corrupted.
Run the following command below for problem mail account:
"%plesk_bin%"\mchk --domain --domain-name=domain.tld