POP vs IMAP email Protocols
Email became critical in day today life. Those days’ even people share computers to check email but these days an individual may have more than one device to check email. POP and IMAP Protocols were introduced by considering all these needs. SMTP (Simple Mail Transfer Protocol) is the protocol used in sending emails and POP (Post Office Protocol) and IMAP (Internet Message Access Protocol) are used in receiving emails from mail server.
POP (Post Office Protocol)
Basically POP is an email accessing protocol used to download emails from central mail server. General email POP clients or applications like MS Outlook and MS Outlook Express will download all emails from the server to the local computer, delete them on the server and then disconnect the connection which was established by TCP and UDP.
Generally POP server uses port 110 to listen to the POP requests but in secure mail services, TLS (Transport Layer Security) or SSL (Secure Socket Layer) will be used to connect to the mail server using STLS command or POP3S. (Port No 995).
Even though there is an option in the mail client to set it to leave the copies of the emails in the server which is not generally being practiced due to various reasons. Those days by considering the mail sever space this method would have been introduced but these days server spaces are in Terra Bytes and that is not at all a constraint.
IMAP (Internet Message Access Protocol)
IMAP is another protocol to access the mails from server. IMAP server listens on port 143 for incoming requesting to deliver the mails. Basically in IMAP protocol, emails will be stored in the centralised server and could be accessible from any clients anywhere. You can just think of it as a remote desktop connection to a server where the email clients like outlook is running on the same machine where the POP server is also running. You just use a window or remote desktop application to view the email client which is running remotely. There are lots of feature and advantages on IMAP when comparing with POP.
(1) Connection to the IMAP Server
In IMAP environment email clients often stay connected with IMAP Server as long as user interface is active.
(2) Multiple Clients and Simultaneous Access
Since mails are stored in the mail server and not like POP once downloaded messages will be deleted here in IMAP server, we can access to the mail window from anywhere at any time.
(3) Access to Partial Message
Mail clients will retrieve text portion of the mail from the server without downloading the whole message or attachments. Further if the user requests the attachment only it will be fully downloaded.
(4) Message Status information
Flags, read mails, replied mails, forwarded mails will be marked and these information will be kept on the mail server itself. If you access those mails from another client also will show the status information.
(5) Mail boxes on Server
IMAP clients can create, delete, rename mail boxes on the server and even deleted mails will be moved to deleted folder on the server itself.
(6) Search performed in Server
IMAP client send the request to perform the search on the server.
Difference Between POP and IMAP
(1) Both are email access protocols where POP downloads the mails in to the local device where in IMAP keeps the mails on the server and provides view from multiple places simultaneously.
(2) POP uses port number 110 and IMAP uses port number 143
(3) POP downloads and disconnects from the server whereas IMAP client is always connected and sends notifications as and when new mail arrives
(4) All the mail folders are in the server in IMAP and in POP it’s in the local device and which is local to the device itself.
(5) In IMAP, if you mark a mail as read or forwarded the status is visible from any IMAP client whereas in POP once you have downloaded the mails into your local device no more access from other devices.
(6) There is an option in POP mail client to set to leave the mails on the server for certain period of time and delete. If you are using 2 clients, set the second client as download mails from server and don’t leave copies on the server.
(7) Virus scans and vulnerability checks are easy in IMAP since the mails are kept on server and scanning will be done in server itself. Whereas in POP, if you download mails to your local device you need to scan all emails.
(8) Search is performed on the server in IMAP whereas in POP, search is performed in the local device.
(9) There are possibilities the local machine or device may crash or lose its data whereas in IMAP mails it will be kept in servers with high availability and redundancy.