SMTP, which stands for Simple Mail Transfer Protocol, is the software that allows you to send out e-mail messages from your email addresses. Without this, you won't be able to use email apps or webmail. Whenever you send an e-mail, your SMTP server connects to a DNS server to determine exactly where e-mails for the recipient domain name are managed. Subsequently, it creates a connection to the remote mail server and exchanges details. If the recipient mail box is present, your server transmits the e-mail to the receiving POP/IMAP server and the latter delivers that message to the specific mailbox where the receiver can access it. If you want to send e-mails, you should always ensure that the website hosting company has the service with their plans. Even though you make use of 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 web form to work.