Microsoft outlook occasionally has an issue with receiving multiple email recipients from external programs like System Five. Even though the format is correct in the address line ( email@example.com; firstname.lastname@example.org ), you may still receive the following error:
The workaround is fairly simple. In System Five, instead of using a semicolon between email addresses, use a comma. Then in Outlook, click on File, then Options. This will open the Outlook Options window. Now click on Mail in the left-hand window, and then put a checkmark in the check box next to “Commas can be used to separate multiple message recipients”.
This list might not be complete due to ACL restrictions and hidden pages.