Use a secure server for quick online order processing and a postal address for them to send their order the traditional way. Spam signals deceit. People are naturally very hostile to and suspicious of unsolicited commercial email. Spamming is a sure fire way to undermine people's trust. Deliver your messages only to people who have initiated communication with you first, either by using one of your services, or by explicitly asking for more information.
Most small businesses rely on word of mouth advertising.
Neighbours and friends tend to talk about their buying experiences, offering recommendations if the service was good, and recriminations otherwise. Trust is liquid, flowing through recommendations and referrals from one satisfied customer to the next. On your website you can harness the power of a personal referral by reprinting the testimonials of your happy customers. When you produce a quality product or service, you will find that people are very willing to write to you expressing their gratitude. E-mail makes it very easy for customers to offer their positive feedback, and you can share that information with others to build their trust.