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Using on POP3/IMAP4

What are POP3 and IMAP4?

This section will give a simple explanation of what POP3 and IMAP4 are. Use whichever one suits you best.

Protocol Strengths Weaknesses
POP3 As it loads server-based emails into the computer, it means that any email you receive can be read again without having to connect to the network. This is suited for times when the connection quality is low. As it needs to be loaded into each computer you use, it does mean that the reception status can vary between computers. If you forget to set it to "Leave on server," you will not be able to load in onto other computers.
IMAP4 As you view emails from the server directly, it uses the same environment no matter which computer you access it from. It can also be linked with the web-based email status. This is suited for relatively stable Internet connections. You cannot view your emails if you cannot connect to the network (some email software will save emails in their cache, meaning you can read them).

About the usage environment

POP3 and IMAP4 both have a number of restrictions when using the new system (Gmail).

  • You can only use POP3s (POP3 over SSL), IMAP4s (IMAP4 over SSL), and SMTPs (SMTP over SSL). For password protection reasons, you cannot use unencrypted POP3, IMAP4, or SMTP. In other words, you cannot use email software that does not support POP3s, IMAP4s, or SMTPs.
  • You need authentication (SMTP auth) when sending emails. Your account and password for this are the same as when receiving emails. You cannot use email software that does not support SMTP auth.
  • pop.gmail.com and imap.gmail.com do not support the changeover to encrypted transmission using STARTTLS.
  • Emails moved to folders other than the Inbox on web-based email cannot be loaded using POP3. If you want to be able to receive these emails using POP3, you will need to return them to the Inbox.

Server information

  Server name Port Protocol Remarks
POP3 server pop.gmail.com 995 POP3 (SSL/TLS)  
IMAP4 server imap.gmail.com 993 IMAP4 (SSL/TLS)  
SMTP server smtp.gmail.com 465/587 SMTP (SSL/TLS) authentication required (SMTP auth)
  • When connecting to Port 465 on smtp.gmail.com, you will need to use SSL/TLS when starting transmission, but when connecting to Port 587, you do not use SSL/TSL when starting transmission, but need to switch to STARTTLS from when you first connect.
  • When setting up your email software, include all of "@keio.jp" in your authentication account.

Update History

2015/03/06: First created

Last-Modified: March 6, 2015

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