The inboxes of your contacts need to authenticate the source of your messages (usually through SPF and DKIM). If you are sending from a Gmail address, Hotmail, Yahoo or any other free webmail, this authentication is impossible and the message may be rejected. This message rejection will cause an error that can affect your deliverability and the reputation of our IP addresses.
This is why you should definitely consider adding a sender address that is linked to your domain name. For example: firstname.lastname@example.org. If you are using a custom domain email, you can then setup SPF and DKIM to help with your deliverability. This will give your emails a better chance of being delivered to the recipient’s inbox… which is what you want, right?