Gmail doesn't support format=flowed, so from that perspective, it too is an old client. Last time I checked, one of the most widely used non-web clients also di

Gmail doesn't support format=flowed, so from that perspective, it too is an old client. Last time I checked, one of the most widely used non-web clients also didn't support it (Outlook). But the good thing about format=flowed is that even if a client doesn't support it for display, it'll still look good (on desktops)