This is not a supported workflow in Formscentral. Email based workflows creating using Adobe Acrobat should be able to do this sort of thing.
Is this because of the field type I'm using? I have another form in which I added an e-mail field type where customer are typing the e-mail of the person who is submitting the form and they are receiving an e-mail submisson receipt based on that e-mail/field.
So, if I change my drop down menu field type to an e-mail field type so the user type their e-mail instead of selecting it from a defined list (saves time) it should work fine, correct?
Email Receipts are sent to the e-mail address identified when you set up the Options for your form. The field it selects from needs to be of the type "E-mail". A drop-down list of e-mail addresses is not of a field type of "E-mail" but is simply a drop-down list. The FormsCentral system does not know, nor has it validated, the data in the field, and so can not send e-mails to the addresses in a drop-down list.
Your form could include a formatted text field instructing people to enter one of the following e-mail addresses in the e-mail address field, and then it would work, but then the person submitting the form would A) not get a copy of their submission to their e-mail address, and B) run the risk of typing in the wrong e-mail address.
A better solution is to have e-mail notifications come to you, or an address you specify, and to have your mail server or client do the processing of those messages. So if, for instance, in the submitted data there was a text string that triggered a mail filter or action when that response came in, the incoming message could then be forwarded by your mail client or the mail server to forward that message to the appropriate recipient.