What is POP3 and which are the default POP3 ports
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. Note, that by default, when you use POP3 to connect to your email account, messages are downloaded locally and removed from the servers. This means that if you access your account from multiple locations, that may not be the best option for you. On the other hand, if you use POP3, your messages are stored on your local computer, which reduces the space your email account uses on your web server. Your email client may have an option to leave messages downloaded on the server for X amount of days, which in this case you would be able to access your messages from multiple locations.
By default, the POP3 protocol works on two ports:
Port 110 - this is the default POP3 non-encrypted port
Port 995 - this is the port you need to use if you want to connect using POP3 securely via SSL encryption.
What is IMAP and which are the default IMAP ports
The 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.
By default, the IMAP protocol works on two ports:
Port 143 - this is the default IMAP non-encrypted port
Port 993 - this is the port you need to use if you want to connect using IMAP securely via SSL encryption.
What is SMTP and which are the default SMTP ports
Simple Mail Transfer Protocol (SMTP) is the standard protocol for sending emails across the Internet.
By default, the SMTP protocol works on three ports:
Port 25 - this is the default SMTP non-encrypted port that email servers use to send to each other. For e-mail program configuration, you cannot use this port.
Port 587 - this port is opened on our e-mail servers for sending non-encrypted emails with SMTP. This port can be used with STARTTLS (TLS), another method of SMTP encryption for sending message securely. This port also requires SMTP authentication to be turned on within your e-mail client.
Port 465 - this is the port used, if you want to send messages using SMTP securely via SSL encryption. This port also requires SMTP authentication to be turend on within your e-mail client.