It works internally as it is configured today, my issue now, since we moved to O365, is sending externally. Previously, when on-prem, we could do this but now since we're O365 it has to match the domain otherwise O365 rejects it. We send Notify Me messages to our ServiceNow platform (hosted) in order to generate tickets for after hours Help Desk calls. I just need to change the @hostname.domain.companyname.com to @companyname.com so O365 lets it through.