Is this your relationship?
Customer::customerID = Flyers::CustomerID
Don't you have cases where the same flyer record needs to be linked to more than one customer?
If the above relationship is what you have, all fields in the related customer records are directly accessible from a given Flyer record and you can refer to them in your Send Mail step in order to send an email to that customer.
But I suspect you need a join table here so that a given customer record can be linked to many flyer records and at the same time be able to link a given Flyer Record to many customer records...
If I'm understanding you correctly than I have the relationship link correct or are both tables linked by their "Keys"?
Doesn't look like the right relationship. How would you link two different customer records to the same flyer?
Or is that something that isn't possible?
In my example, CustomerID would be defined as a serial number field in the customer table and as a number field in the Flyers table. This makes it possible to link many Flyers records to the same customer but the reverse is not possible. If you need to be able to link many customer records to the same flyer and also to link many flyers records to the same customer--which is what I imagine to be the case--you need a third table so you can set up a many to many relationship here.
Ok, I admit that I'm a novice when it comes to this can you please show me what I need to do to create this properly? What kind of table do I need? Is this like how the invoiceing system works.
Do you have a many to many relationship? In other words, do you need to link multiple contacts to multiple flyers?
If so, then yes, the lineItems table in the starter solution is an example of a join table where you can link many invoices with many products.
Here also, is a demo file illustrating the basic set up for many to many relationships plus some more sophisticated interface designs that you can examine and consider: http://www.4shared.com/file/dZ0bjclw/ManyToManywDemoWExtras.html
The demo file has a lot of commentary added on the layouts, in field comments and in Manage | Database | relationships.
It's also fairly new so feel free to ask questions about it if there's a part of it that you don't understand. (I recently updated this file in response to questions by two other posters to add additional commentary.)