How to manage automated emails sent from a web application

Question

I am designing a web application and I am wondering how to design the architecture to manage sending automated emails.

Currently I have this feature build into my web app and the emails are sent based on user input / interactions (like creating a new user). The problem is that connecting directly to a mail server takes a couple of seconds. Scaling my application up, this will be a significant bottle neck in the future.

What is the best way to manage sending a large amount of automated emails within my system architecture?

There won't be a huge amount of emails sent (2000 a day max). Emails don't need to be send immediately, up to 10 mins lag is fine.

Update: Message queuing has been given as an answer, but how would this be designed? Would this be handled in the app and processed during a quiet period, or do i need to create a new 'mail app' or web service to just manage the queue?