Securing one domain and all of your subdomains is easy with the Comodo Premium SSL wildcard SSL certificate. This certificate will protect www.yourdomain.com and all of the associated subdomains like mail.yourdomain.com, abc.yourdomain.com, etc. Also, since this is an Organization Validated (OV) certificate, it will help enhance the trust in your website by activating imagery like "https", the padlock icon next to the URL, and the Comodo Site Seal, which will display real-time company data when a user clicks it. This wildcard SSL certificate is an excellent option for medium-sized companies and ecommerce sites that wish to bolster the trust their users will have with them.
A wildcard SSL certificate protects one main domain along with an unlimited number of subdomains. So, you can use the Comodo Premium SSL Wildcard to protect www.domain.com and payment.domain.com, mail.domain.com, example.domain.com, etc.