Having trouble with notifications coming from ServiceNow not being able to send to emails outside of our company. For example, if I add an email address firstname.lastname@example.org to one of our technicians profile, this person does not get the email. Notifications only work internally with the email addresses being a part of our domain.
Look at one of the emails you do receive from the system, specifically at the full headers. The ServiceNow system for some inexplicable reason includes headers that tag the emails as autogenerated, spam, etc. and this can cause the external system to block the emails. We had this problem when trying to get ServiceNow to send emails to Zendesk.