I've found what was the problem: in my SendGrid account there was Link Branding enabled. But that's little bit strange because it was enabled before moving to the new server and it worked fine.
I am testing on my forum. So i have create an new user. Because an typo the mail address was wrong. So no validation email. Ok, no problem. I go to admin panel and will send an new validation email, but....
I think this can be better solved.
Just to confirm, you tried to send the confirmation email as an admin and got this error? I think we should allow admins to bypass the time limit.
Yes, send email as admin.
@baris Have we given any thought to the havoc such could wreak on the Internet at large when an admin account becomes compromised? Maybe not such a bad idea to enforce some minimal delay?