When attempting to create a filter for an organisation or user with multiple sender/recipient email addresses or domains, you may receive an error after clicking the ‘Save Filter’ button:
Email address pattern ‘example@example.com, *@example2.com’ contains invalid characters
To resolve this error, in the ‘Filter Builder’ section of the Filters page, click on second drop down box under If condition – the drop down list will have number of states – IS, IS NOT, IS ANY OF, IS NONE OF. In this instance, as there are multiple email addresses/domains being used in the rule, ensure you have selected the operator ‘IS ANY OF’ or ‘IS NONE OF’ (as appropriate to your rule).