Fairly new to the email world but have discovered that my email gateway does not like emails with these routing characters in their addresses. Incoming messages with sender addresses such as !firstname.lastname@example.org receive an NDR 550 Denied by Policy. It's taken me a while to figure this out too because I don't see message logs regarding blocks due to this reason. Is there a way to enable logging for Denied routing character blocks? Is there a way to "whitelist" IP ranges or domains regarding these routing characters? What would I really be allowing them to do if I could?
"!", "%", "|"