IMAP vs POP3: Which Should I Use?
When you add a Kapsule mailbox to a mail app it asks whether to connect over IMAP or POP3, and for almost everybody the correct answer is IMAP.
The two protocols solve the same problem in opposite ways. IMAP treats the server as the master copy of your mail and every device as a window onto it. POP3 treats your device as the master copy and, by default, empties the server behind it. That single difference decides everything else, including whether losing a laptop also loses ten years of email.
The Short Answer
Choose IMAP. Kapsule mailboxes are built around it: webmail, the mobile setup profiles, and every settings panel in KPanel all assume IMAP, and your mail stays on the server where it is backed up and reachable from anything.
Choose POP3 only if you have a specific, deliberate reason, and you know what you are giving up.
How IMAP Works
IMAP keeps every message on the server and synchronises state in both directions. Read a message on your phone and it shows as read on your laptop. File it into a folder on your desktop and the folder is there in webmail. Delete it anywhere and it is gone everywhere.
Use IMAP if you:
- Read email on more than one device, which today is nearly everyone
- Want webmail to show the same mailbox as your mail app
- Want your mail to survive a lost, stolen or wiped device
- Use folders, labels or server-side filters to organise mail
IMAP Settings
| Setting | Value |
|---|---|
| Server | mail.kapsulehost.com |
| Port | 993 |
| Security | SSL/TLS |
| Username | Your full email address |
| Password | Your mailbox password |
Outgoing Mail (SMTP)
Whichever protocol you pick for receiving, outgoing mail always goes over SMTP:
| Setting | Value |
|---|---|
| Server | mail.kapsulehost.com |
| Port | 465 |
| Security | SSL/TLS |
| Username | Your full email address |
| Password | Your mailbox password |
The username is always the FULL email address, you@yourdomain.com, never just the part before the at sign. Getting this wrong is the single most common cause of "authentication failed" when adding a mailbox by hand.
You do not have to copy these from an article. KPanel shows them on the mailbox itself: open Email in the left sidebar, click the mailbox, and go to the Setup tab, where IMAP (incoming mail) and SMTP (outgoing mail) are listed with a copy button on every field.
How POP3 Works
POP3 downloads messages to one device and, in its default configuration, deletes them from the server as it goes. After that the mail exists in exactly one place. Nothing syncs: read and unread state, folders and deletions all stay local to that machine.
With POP3 in its default setting, your mail is on one device and nowhere else. If that device is lost, stolen, wiped or simply dies, the mail is gone, and Kapsule cannot restore what the server was told to delete. Webmail will show an empty mailbox, because as far as the server is concerned it is empty.
Genuine reasons to pick POP3 are rare, and they are all variations on "one machine, no sync, and I am running my own backups":
- A single desktop that is the only place this mailbox is ever read, backed up locally
- An archive workflow that deliberately pulls mail down into another system
- A legacy application that speaks POP3 and nothing else
POP3 is available on Kapsule mailboxes for those cases. The Setup tab lists IMAP and SMTP only, because those are what we recommend and support first. If you have a real need for POP3, open a support ticket and we will give you the exact settings for your mailbox.
If you chose POP3 because you were worried about filling your mailbox quota, switch to IMAP and manage the quota instead. Deleting large attachments, emptying Trash and Junk, and archiving old years are all far safer than a protocol whose whole design is to remove your only copy from the server.
Webmail: The Third Option
You do not have to configure anything at all. Kapsule Mail includes browser-based webmail at webmail.kapsulehost.com, and KPanel can sign you straight in with Open Webmail on the mailbox page. Webmail reads the same server-side mailbox as IMAP, so everything stays in sync with your other devices. See Accessing Your Email via Webmail.
Comparison
| IMAP | POP3 | Webmail | |
|---|---|---|---|
| Where mail lives | On the server | On one device | On the server |
| Syncs across devices | Yes | No | Yes |
| Survives losing your device | Yes | No | Yes |
| Works offline | Yes, after sync | Yes | No |
| Folders and read state shared | Yes | No | Yes |
| Setup required | One time per device | One time per device | None |
| Recommended | Yes | Only for a specific reason | Yes |
Switching From POP3 to IMAP
If a mailbox is already set up as POP3 and you want to move to IMAP, the order matters, because your only copy of the mail is currently on your device.
- In your mail app, find the POP3 account's advanced settings and turn OFF "delete messages from server" if it is still enabled, so nothing more is removed.
- Add the mailbox again as a NEW IMAP account using the settings above. Do not delete the POP3 account yet.
- Wait for the IMAP account to finish its first sync.
- Drag or copy the messages from the old POP3 account's local folders into the new IMAP folders. They upload to the server as you do.
- Only once you can see everything in webmail, remove the old POP3 account.
Never delete the POP3 account before its mail has been copied into the IMAP account and confirmed in webmail. Removing a POP3 account in most mail apps removes its local store, and that store is the only copy in existence. There is nothing on the server to restore from.
Troubleshooting
"Authentication failed" or "wrong password". Use the full email address as the username, and remember that the mailbox password is separate from your KPanel sign-in password. Reset it under Email, then the mailbox, then the Password tab.
The app cannot connect at all. Confirm the port and that security is SSL/TLS. Some networks block outbound mail ports: try a phone on mobile data as a quick test. Port 465 for sending and 993 for receiving are the only combinations we support.
My phone shows old mail but nothing new. The account was likely added as POP3 rather than IMAP. Check the account type in your mail app settings.
Mail disappeared from webmail after I set up a mail app. A POP3 client downloaded and removed it. Check that device.
I just created the mailbox and it will not connect. Give it a few seconds to finish provisioning, then check the status reads Active on the mailbox page in KPanel.
Related: Setting Up Your Mailbox, Configuring Your Email in Outlook, Apple Mail and Mobile, Setting Up Email on iPhone and Android, and Email Not Receiving.