IMAP vs POP3 is the first choice you make when adding an email account to Outlook, Thunderbird or a phone. Both let a mail app read messages from a mail server, but they treat your mailbox very differently. This guide explains the difference and which to pick.
Before you start
You need an email account and its incoming server name. On MdmHost cPanel hosting you find the settings in cPanel → Email → Email Accounts → Connect Devices.
How IMAP works
IMAP (Internet Message Access Protocol) keeps mail on the server and syncs a view of it to each device. Reading, deleting or moving a message on your phone shows up on your laptop and in webmail too. Folders such as Sent and Drafts are shared across devices.
How POP3 works
POP3 (Post Office Protocol version 3) downloads messages to one device. By default it then deletes them from the server, although most apps offer "leave a copy on the server". It does not sync read status or folders.
IMAP vs POP3 compared
| IMAP | POP3 | |
|---|---|---|
| Where mail lives | On the server | On the device (usually) |
| Multiple devices | Fully synced | Poor – each device downloads separately |
| Folders | Server-side, shared | Inbox only |
| Server storage use | Grows over time | Low |
| Offline access | Cached copies | Full local copy |
| Secure port | 993 (SSL/TLS) | 995 (SSL/TLS) |
| Plain/STARTTLS port | 143 | 110 |
Sending always uses SMTP, usually on port 465 (SSL/TLS) or 587 (STARTTLS), whichever incoming protocol you choose.
Which should you use?
- IMAP for almost everyone: phones, laptops, webmail and shared mailboxes stay in sync, and the server's backups protect your mail.
- POP3 only if you use a single computer, want mail stored locally, have very limited server quota, or need to archive mail off the server.
Switching from POP3 to IMAP
- Make sure the messages you need are still on the server, or plan to upload them.
- Add the account again in your app using IMAP (most apps cannot convert an existing account).
- Drag old local POP3 folders into the IMAP account to upload them to the server.
- Remove the old POP3 account once everything is copied.
Troubleshooting
- Mail disappears from webmail: a device is using POP3 without "leave a copy on server".
- Mailbox full on IMAP: empty Trash and Junk and archive old mail.
- Certificate warnings: use the server hostname your host provides for SSL connections.
FAQ: IMAP vs POP3
Is IMAP more secure than POP3?
Both are secure when used over SSL/TLS on ports 993 and 995. The protocol choice is about syncing, not security.
Can I use IMAP and POP3 on the same account?
Yes, but a POP3 client that deletes downloaded mail will remove it for IMAP devices too.
Does IMAP use more server space?
Yes, because mail stays on the server. Keep an eye on your mailbox quota.