Not all users of a O365 environment can be joined to a domain that is part of the O365 infrastructure. Many of us use a website OWA access that belongs in a government domain, but are required to use their o365 email for all communication. Edge and Chromium SMIME extensions must work for external computers that are not joined to the domain, since millions of our corporate computers will never be joined to these domains. We remain stuck to 32bit Internet Explorer for SMIME. Either remove the domain requirement, take on the acceptance and control of domains that are acceptable to our customer, or fully deprecate SMIME.