Hi IAN TAIT 

Do you know what version of Studio (if any) your client is using and why they would need a TMX?                                                                                              Any information on why they cannot 'read' the TMX would be helpful.

As the name suggests- a server based TM is created and stored on a server, you cannot create a server TM and send this as an attachment.

Did the client send you a TM within the original project? or have you created your own TM?

My guess is that it's another, uhm, totally unexperienced user (hope this expression survives the censorship) who "cannot read TMX" simply because after clicking on the "Open" TM button the dialog displays only SDLTMs... and clicking on the file type dropdown is way beyond the user's capabilities...
The amusing requirement for sending a server-based TM as attachment pretty confirms that assumption.

This is by the way another UX glitch... there is apparently no reason why the default filter would not be the usual "All supported Translation Memory formats" and displaying files of all supported types.

Well Evzen Polenka , this is exactly why we have this forum. It's not just for experts and you have to start somewhere!

Sometimes the way you help people is the most important part of helping them in the first place, so if it's not possible to do this in a constructive way then it may be better to restrict involvement to the more challenging aspects of working with the tools.