POP3 vs IMAP

POP3 vs IMAP: the one-line difference

IMAP leaves the mailbox on the server, so every device works on the same copy. POP3 downloads mail to one device and deletes the server copy after the download unless you switch that off. Use IMAP by default; choose POP3 only for a single machine, an offline archive, or a mailbox quota you cannot raise.

Both protocols do the same first job: prove the user's identity and hand over the messages waiting in the mailbox. They differ in what happens afterwards. POP3 treats the server as a delivery van that empties. IMAP treats it as the filing cabinet that every client reads from.

• IMAP: folders, read flags and deletions happen on the server and every client sees the result.
• POP3: the client decides locally what to keep, and the server forgets.
• Neither protocol sends mail. Sending is SMTP, covered in what SMTP does.
• Both can run encrypted: IMAP on 993, POP3 on 995.

How POP3 downloads mail to one device

POP3 opens a session, authenticates, lists the waiting messages, retrieves them, and then marks them deleted. The whole conversation is a short set of text commands: USER, PASS, STAT, LIST, RETR, DELE and QUIT. That smallness is why POP3 runs on printers and old handsets that could never hold an IMAP cache.

The delete step is the part people miss. Some clients delete on download, some after a set number of days, and some never. Look for "leave a copy of messages on the server" in the account settings before you migrate anything. If a phone has been collecting the same mailbox for years, the messages may already exist only on that phone.

With leave-a-copy on, POP3 becomes a one-way sync. New mail still reaches the server, so a second device can fetch it, but folders, read state and sent items stay where they were created and never travel back.

How IMAP keeps one mailbox across devices

IMAP leaves every message on the server and syncs the state around it: which folder holds it, whether it is read, flagged or answered, and whether it has been deleted. A phone that connects an hour later sees the same tree, in the same order, with the same unread count.

The cost is storage and a little patience. Every attachment stays on the server until somebody deletes or archives it, so a shared mailbox fills faster than a POP3 one. Clients cache headers and usually bodies, but a search across tens of thousands of messages still asks the server, and the list appears before the message body on a slow link.

On cPanel mailboxes, IMAP is on by default and needs no extra setup. The same hostname works for both protocols: your mail domain, port 993 for IMAP, 995 for POP3.

POP3 and IMAP compared, feature by feature

Read the table by consequence, not by feature name. Each row changes something a user will notice within a week.

A mailbox with 5 GB of quota behaves differently on each protocol. On POP3 it never fills, because the mail is not kept. On IMAP it fills once, and after that every sender gets a bounce until somebody archives.

Ports and encryption for each protocol

Use encrypted ports for every connection, including on a home network. The unencrypted ports still work on most servers and still send the password in clear text.

• Incoming IMAP: your mail hostname, port 993, SSL/TLS.
• Incoming POP3: your mail hostname, port 995, SSL/TLS.
• Outgoing SMTP: port 587 with STARTTLS, or 465 with SSL/TLS on older clients.
• Username: the full email address on a cPanel mailbox, not the part before the @.
• Plain ports 110 and 143: only inside a trusted network, and never with a reused password.

If port 993 is blocked, try 143 with STARTTLS before you decide the server is down. Office and campus firewalls in India block 993 more often than they block 143, and STARTTLS gives the same encryption over the other port.

When POP3 is still the right choice

POP3 is not obsolete. It is the wrong default, which is a different thing. Five cases still call for it.

• One device and one mailbox: there is nothing to keep in sync, so there is nothing to drift.
• A quota you cannot raise, where mail must leave the server to stay under the cap.
• A metered or unreliable connection: download once, read offline, never re-fetch.
• A record-keeping rule that requires mail to sit on a machine the business controls.
• A role address such as accounts@ where one person is meant to take the mail away.

None of those justify POP3 for a team. The moment a second person or a second device opens the mailbox, POP3 hands somebody a partial copy and nobody can tell which copy is complete.

Move from POP3 to IMAP without losing mail

The move is safe when the old account stays in place until the new one has finished syncing. Do it in this order.

1. Export the mailbox from the client first. In Outlook that is File, then Open & Export, then Import/Export, then Export to a file. Name the file with the date.
2. Confirm IMAP is enabled for the mailbox in cPanel under Email Accounts, then Connect Devices, which lists the hostname and ports.
3. Add the same mailbox to the client as a new IMAP account on port 993. Leave the POP3 account in place and do not let it delete anything.
4. Wait for the first IMAP sync to finish, then drag the local POP3 folders into the IMAP tree. Outlook users importing a PST should create the destination folder on the server first, then import into it, or the mail lands in a local folder that never syncs.
5. Send a test message from another address and confirm it appears in webmail and on the phone. Keep the POP3 account disabled but present for 30 days.

You know it worked when a message read on the phone shows as read in webmail, and the Sent folder on both holds the same items. If Sent is still empty on one device, the client is saving sent mail locally instead of to the server folder.

WebJi® business email supports both protocols on the same mailbox, so this is a client change, not a plan change. Mailbox sizes and prices sit on business email hosting. If the whole mailbox is moving to a new host as well, start from moving mailboxes to a new host.