I tried searching and came up kind of empty. I read a comment the other day that said NOT to use safe-mail and another person backed them up. But they never said why and now I can't find the comments.
A few vendors that I've used also use safe-mail as their alternate contact. So why is it bad? As long as PGP is used with TOR & TAILS, I don't see why it would matter anyway.
It mostly shouldn't,
You might also consider SIGAINT. Since you can only access your email account via their Tor hidden service, it's impossible to link your account to your home IP address by accidentally reading your email via a clearnet browser.
Go to http://sigaint.org/ to get their onion address.