Sending single mail using mailchimp API V3

We need to send single mail using MailChimp. Is there any provision in MailChimp to send mail without creating list.

According to my understanding we need to :

Create campaign
create list
Map list to campaign

So in case of say successful registration, do we need to follow these steps to send single mail or is there some workaround to avoid these many api calls.

Any help appreciated.

How do I send an email to a few people in Mailchimp?

Send to groups from the campaign builderIn the To section, click Add Recipients. In the Audience drop-down, choose the audience you want to work with. In the Segment or Tag drop-down, choose Group or new segment. Click New Segment.

The Mandrill product (part of MailChimp) is intended for those kinds of one off emails. They call them "transactional" emails since they are based on the user's action.