Custom Process - Error with SendMailingToContact

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Hi,

I have a custom process to send an email to the contact with some information not related to any incident or opportunity, so I have the following code

use RightNow\Connect\v1_2 as RNCPHP;
RNCPHP\Mailing::SendMailingToContact($Contact, null, 4222, time());

But that function is falling with error -100030001. Any idea how to resolve that?

Thanks.