SMTP, which is an acronym for Simple Mail Transfer Protocol, is the software that enables you to send messages from your email addresses. Without this, you won't be able to use e-mail apps or webmail. Every time you send an email, your SMTP server connects to a DNS server to discover where the emails for the recipient domain are taken care of. Subsequently, it connects to the remote email server and exchanges details. In case the recipient mail box is available, your server sends the email to the receiving POP/IMAP server and the latter delivers that e-mail to the specific mailbox where the receiver can find it. If you would like to send emails, it is recommended to ensure that the hosting company offers the service with their packages. Even when you make use of online form that visitors use to contact you, you still require an active SMTP server for your hosting account for the web form to work.