If you have a coupon for a free trial account, if it is active you should be able to apply it in the sign up form. There are a few things to know about Trial Accounts:
1. 5 Outgoing Emails Per Day - The only true limitation that trial accounts have is how many emails they can send out. At this time we limit trial accounts to 5 emails per day to cut back on the risk of someone coming in to abuse our system and damage the reliability of our domains. Other than that, you can look around and set things up and make sure it's right for you.
2. Credit Card is Required - Another thing that helps us combat abuse and fraud is that a credit card is required to sign up even if you have a free trial code. Don't worry, though! If you decide that our service isn't for you during your trial period, you will not be charged. Please remember that if you want to cancel during your trial, you must do so BEFORE the trial ends so our system won't charge you. It's automatic.
3. Upgrading During the Trial - If you decide that you want to keep the account early and want to lift the restrictions, simply email us at email@example.com and let us know you want to end your trial. Your credit card will be charged and your account will be opened up for full use.
If you have any further questions, please feel free to let us know! You can send an email to firstname.lastname@example.org or fill out the form here at the knowledge base to open a support ticket that way.