If you have a Gmail account, emails can sometimes land in the Promotions tab, here is how to change that.
Tip: You can do so by either dragging and dropping the message into the Primary tab, or by moving it using the Move to tab feature.
Once the message has been moved, Gmail gives you the option to always have such messages delivered to that tab.
Tip: If you use a spam blocker, it can make it difficult for our emails to reach you. If you don't receive a message, check your junk and spam folder to see if it may have gone there. If the email is showing up there, please mark the campaign as "not spam" and us to your Contacts.
This will encourage delivery to the in-box.