Can't view MSG or EML files
If you attach an email message (.msg or .eml file) to a message in Outlook synced with GSSMO or IMAP, recipients using Microsoft Exchange will not be able to read the attachment (the attachment appears blank). To avoid this issue, it is best to forward the message itself via Outlook, rather than attach a message as a .msg or .eml file.
Notice also that Gmail does not convert .msg or .eml attachments. In particular if the sender of a message wants the forwarded message in format .msg/.eml to be readable by recipient on Gmail, proper conversion of it into MIME type message/rfc822 must be done. GSSMO can convert such attachments into message/rfc822. With this in mind consider the following scenarios.
Outlook > GSSMO > Google Mail Servers > Gmail UI
If a GSSMO user sends an .msg/.eml attachment through Outlook, a recipient in Gmail Web UI will see the message as noname.eml and the attachment will be readable. The reason why the user can see message content in Gmail Web UI is because EMAPI> MIME type message/rfc822 conversion was done internally by GSSMO itself.
Outlook > GSSMO > Google Mail Servers > GSSMO > Outlook
A .msg/.eml attachment sent by a GSSMO user to another GSSMO user will be received in .msg/.eml format without name change as it’s not affected by the above mentioned issue and readable since again GSSMO will convert EMAPI to MIME type message/rfc822.
Outlook > Google Mail Servers > Gmail UI
If a .msg/.eml attachment is sent through Outlook and received in Gmail Web UI, the attachment won’t be converted by GSSMO from EMAPI to MIME type message/rfc822 and therefore won’t be readable.
Again, in order for it to be readable, there must be something in the delivery path from the user to the Google Mail servers that will transform the attachment from EMAPI (.msg) format into MIME message/rfc822.