SMTP, which is short for Simple Mail Transfer Protocol, is the software that allows you to send out messages from your email addresses. Without it, you won't be able to use e-mail applications or webmail. Every time you send a message, your SMTP server connects to a DNS server to determine where the e-mails for the recipient domain are taken care of. Following that, it connects to the remote mail server and trades information. In case the recipient mailbox is present, your server transmits the e-mail to the receiving POP/IMAP server and the latter brings that e-mail to the specific mailbox where the recipient can get it. If you want to send emails, it is recommended to make sure that the website hosting company provides the service with their packages. Even though you work with an online form that website visitors use to get hold of you, you will still require an active SMTP server for your hosting account for the form to work.