Auto-reply in Plesk > Subscriptions > domain.tld > Mail > email@example.com > Auto-Reply > Switch on auto-reply is enabled, however auto-reply messages are not get sent.
Autoresponder that is set via MailEnable Admin panel works properly.
MailEnable server SMTP security misconfiguration.
Change SMTP settings using the following steps:
Make sure that installed MailEnable version is supported by Plesk.
Launch MailEnable Management Console
Go to Servers > Localhost > Services and Connectors > SMTP > Right Click > Properties
Select Security tab and disable options
Disable all catchallsand
Authenticated senders must use valid sender address
Click Apply button, but do not close Properties window.
Go to Relay tab > Privileged IPs... > Granted relay rights
Press Add , input the mail server outgoing IP address and click OK .
Mail server outgoing IP address can be found in Outbound tab > Outbound IP Binding
MailEnable SMTP Connectorservice:
net stop "MailEnable SMTP Connector"
net start "MailEnable SMTP Connector"
NOTE: According to current business logic it is not possible to use both Plesk auto responder and option "Authenticated senders must use valid sender address" enabled. As workaround enable the option and use autoresponder of Mail Enable.