I set up an email sequence and it's accompanying automation. However, some of my subscribers are receiving the emails and others simply didn't get them - why? Everything is set up properly and the emails didn't go to span - the just flat out were never received. Why is this and how do I fix it? If it makes any difference, half gmail users received them and half didn't. Hotmail users didn't get them but yahoo did as well as hey.com. The sequences are not paused and are set up sequentially. The automation is turned on. What else do I need to do??