To get accepted by turboSMTP you need to use a From email address hosted at a domain that you own and can access. This will help keep your campaigns out of spam folders and protect the reputation of you, the sender, by ensuring others can’t use your domain without permission.

If you use a free domain (Gmail, Hotmail, etc.) as your From email address, you can't configure your DKIM and SPF to get the highest deliverability; that's why we recommend to use only a personal domain and configure both the aforementioned records; and that's why we don't allow to register with a free email account.