Occasionally it may appear that your email is queued and waiting to be delivered. There are a few reasons for this: -
1. The email sender runs every few seconds so there is little delay, but sometimes you're campaign is just caught in the middle of this, this normally happens when you have a large volume of contacts to send to and you have used a lot of personalisation which the system needs to add (it still only takes a few seconds though!)
2. There is a high volume of emails going out at that moment in time, we try and send as many emails as we possibly can for customers, regardless of their list size, but sometimes some big campaigns coming in together (IE 500,000+ campaigns), so we clear it down as fast as possible.