As part of security policy our central smtp server doesn't accept e-mail messages containing executable files. SOGo uses this smtp server.
When user sends message containing executable file, smtp server rejects it and SOGo shows white "Warning window":

Warning
cannot send message: (smtp) failure when sending data

User considers it for fault of the service and he knows nothing about the right reason.
Smtp server rejects that message with detail "5.7.1" warning - see log:

Nov 28 00:02:36 fred postfix/cleanup[3174]: 0CDD4300C6341: milter-reject: END-OF-MESSAGE from webmail.zcu.cz[147.228.57.30]: 5.7.1 This message was blocked because its content presents a potential security issue. Please visit http://mail.zcu.cz/policy/ to review our message content and attachment content guidelines. Tato zprava byla zablokovana, protoze jeji obsah predstavuje potencialni bezpecnostni problem. Prosim navstivte http://mail.zcu.cz/policy/ pro blizsi informace.; from=<harryp@civ.zcu.cz> to=<harryp@civ.zcu.cz> proto=ESMTP helo=<webmail.zcu.cz>

So it would be very useful when SOGo will show that "5.7.1" warning in its "Warning window" in the same way as native e-mail clients do.

Thanks