Unable to access remote CMAIL

[siglocero]

Hi there,

whenever we try to access the remote CMAIL via the Remote Mail button (on the Plesk panel), a warning says:

Warning: Unable to access the remote service for this domain. The most common reason is that the service for this domain is not activated yet. Please, wait for several minutes, and then try again. If you encounter this error again, contact your system administrator.

Some domains work perfect, but in this case, this one has this trouble.

Any suggestions?

Thanks in advance.