Using a custom email address, rather than gmail or hotmail will improve open rates as users typically assume that this email has come from a trusted source.
When you correspond with a potential client by email, they’ll know that you take your business serious since you are not on a free gmail or hotmail email . The same is true if someone forwards one of your emails.
Having a personalized domain email address, it is easier for people to contact you. Your customers will find your email address easier to remember when they need it. As long as they know your domain name, they can remember your email address.
You can also separate your incoming email by its purpose. Having addresses like John@ThisName.com, Shopping@ThisName.com, Bills@ThisName.com and Spam@ThisName.com can help you compartmentalize your incoming emails.
A personalization email address is also recovered a lot easier then a free one if you get hacked. You own the domain so you can change your password much easier than trying to contact tech support on a free email service.
Lastly, with some email addresses like @att.net and @comcast.net , you can’t take them with you if you switch internet providers. You can maintain consistency and an appearance of reliability when you have a custom email address that you can take with you no matter what.