Post Office Protocol version 3 (POP3) is a standard mail protocol used to receive emails from a remote server to a local email client. POP3 allows you to download email messages on your local computer and read them even when you are offline. Because your messages are stored on your local computer you reduce the space your email account uses on your web server. Note, that when you use POP3 to connect to your email account, messages are downloaded locally and removed from the email server. This means that if you access your account from multiple locations or devices you should probably use IMAP.
Internet Message Access Protocol (IMAP) is a mail protocol used for accessing email on a remote web server from a local client. IMAP and POP3 are the two most commonly used Internet mail protocols for retrieving emails. Both protocols are supported by all modern email clients and web servers.
While the POP3 protocol assumes that your email is being accessed only from one application, IMAP allows simultaneous access by multiple clients. This is why IMAP is more suitable for you if you’re going to access your email from different locations or if your messages are managed by multiple users.
Simple Mail Transfer Protocol (SMTP) is the standard protocol for sending emails across the Internet. Examples include sending emails from your website or accounting software using your domain branded email address.