SMTP, which is short for Simple Mail Transfer Protocol, is the software that allows you to send e-mails from your email addresses. Without it, you will not be able to employ email apps or webmail. Every time you send an email, your SMTP server creates a connection to a DNS server to find out where the e-mails for the recipient domain are handled. Following that, it connects to the remote mail server and exchanges information. In case the recipient mailbox is accessible, your server sends the email to the receiving POP/IMAP server and the latter brings that email to the specific mailbox where the receiver can get it. If you want to send e-mails, it is best to make certain that the web hosting company offers the service with their packages. Even if you use an online form that website visitors use to make contact with you, you will still need an active SMTP server for your hosting account for the web form to work.