Reason #2: Brand Recognition
Adding your domain name to your email address improves your brand recognition. Do you work for Google? Hotmail? Yahoo? AOL? Verizon? No? Then why are you advertising for them with your email address? Make your email address work for your brand and not someone else’s brand. I understand that the Gmail account is free, but you want to look like you take your business seriously, and having a branded email address can help with that.