> If all the servers have to be updated to do this, is it really that much more difficult to just switch to a new protocol entirely to be secure by default? Th

> If all the servers have to be updated to do this, is it really that much more difficult to just switch to a new protocol entirely to be secure by default? The 80:20 solution here might be for the big email providers to declare a flag day (maybe with a 2 year countdown) saying that any email server they connect to after that date has to support TLS, or they will delay the processing of emails to/from that server by 5 minutes, doubling every 6 months. Also, such servers will be named and shamed in their webmail interfaces, so users get a nasty red warning whenever you try to send an email to an affected address or receive one from it. I bet the problem would actually be 99% solved before the flag day even arrived, and most of the remaining 1% would be spam anyway.