Many SMTP servers have delayed delivery for untrusted source servers (eg. via greylisting or any other spam checking system). I'd certainly bail if I had to wa

Many SMTP servers have delayed delivery for untrusted source servers (eg. via greylisting or any other spam checking system). I'd certainly bail if I had to wait 3-15 minutes for my password to arrive before I can enter it on... where was that tab? Anyway, this is just a theory, and I am not sure you can easily (dis)prove it due to the nature of SMTP, but perhaps do a small scale experiment where you allow a subset of users to set their password, and see if the drop off rates are identical?