That might not be greylisting like I'm thinking of, Gmail has its own secret process but in my experience they accept the message and decide if they want to deliver it or not later.
If you don't have a ton of users you don't have the "celebrities getting hit thousands of times with password reset requests" problem and if you do have tons of users, your higher volume of transitional emails makes Gmail trust you more so your issue is much less likely to happen.
