To create a reply email to an email originally sent from Hub, there are two options. 

1. You can just reply in your mail client, such as Gmail. This is used to reply to prospects that emailed you back. Your replies are tracked in Hub if you have a connected Gmail account. 

2. You can draft a reply in Hub, copying the original email, adding "Re: " to the subject, and starting every line of ~70 characters with a ">" (advanced). This is used to create a reply if someone does not engage with your first email.