I would not be good with publishing my PMs publicly, but I can trust @qwk and send him a PM with a screen shot of my PMs from 2012 ( oldest once) which include my original email mentioned. And later he could confirm, what is my original email from much years.
Screenshots don't prove anything. If you want to prove ownership of an email address from an old PM, you could report the PM to Global Mod hilariousandco (after all, his alt started this topic) to verify the address shows in that PM.
However, it's not uncommon for email addresses to change hands together with a Bitcointalkaccount, either when the email gets hacked, or when the account gets sold, so it doesn't really prove anything.