[SalesForce] Is it possible to call external webservice(API) in ExactTarget

Often times when there are issues like this it is being caused by your Contact Builder setup. I notice that you are using Email Address relating to Email Address. Instead try updating this to:

Contact Key to Email Address. Ensure this is a One to One relationship and once that is updated check the box for Use as Root.

At that point, clear the data from your data extension, re-add the rows and re-run your fire event. The reason for this need is the fire event evaluates data by the row number rather than the actual data in the DE. By clearing the data in the data extension and re-adding the data you actually create new rows of data which are then up for evaluation by the trigger.

The reason we need to update the relationship to Contact Key to Email Address is Contact Key is a required field for the Contact being created for the interaction to evaluate.

One other tip, if you want brand new subscribers to be injected into the interaction (by brand new I mean ones that don't exist on your all subscribers list) go to Contacts Configuration within Contact Builder and under the Channel Address Order click edit under the email box and then add address. Select your data extension linked in Contact Builder and save this. This tells the interaction if the subscriber doesn't exist in the account look in this data extension for it.

I hope that helps!

For simplicities' sake, the second option is the way to go. I understand it can be a bit 'clear as mud'. :)

Fire Events point to a sendable DE.

That sendable DE should be in the contact model (Contact Builder) as a 'root' data source. Generally you'd like it mapped 1:1, though that is no longer a requirement. Unless you've got a specific use case for 1:n, i'd just stick to 1:1 by default.

The Sendable DE is mapped to the journey via the Event Administration (formerly Trigger Administration) in Journey Builder - a simple way to do it is to have the event criteria map 'where email address is not null' - effectively, inject all subscribers who are new in the DE (since the last fire event).

All that said, as of last release, fire events are no longer required - you can configure all of that stuff in Event Administration directly in Journey Builder: Event Administration

You can select the data sources from what is configured in Contact Builder, Define how often to inject new subscribers, and what criteria a subscriber has to meet to enter the Journey.