IMAP vs POP3 vs SMTP: which email protocol should you use?

Email uses two kinds of protocols: SMTP sends your mail, and IMAP or POP3 receives it. IMAP keeps your messages on the server and in sync across all your devices, while POP3 downloads them to a single device. If you read email on both your phone and your computer, use IMAP; with LJPc hosting, all three run encrypted through ljpc.email.

This guide covers what each protocol does, how an email travels from sender to recipient, the differences between IMAP and POP3, how to switch from POP3 to IMAP, and where newer options such as JMAP and Exchange fit in.

What are the email protocols?

A protocol is a set of rules that lets programs talk to each other. Every email app relies on three of them:

So to receive email, you choose between IMAP and POP3. To send, you always use SMTP, whichever of the two you pick. All three date back to the 1980s and are still maintained: the latest version of IMAP, IMAP4rev2, was published in 2021 as RFC 9051.

How an email gets from sender to recipient

A single message uses every protocol, plus one DNS record:

1. You click Send. Your email app signs in to the outgoing server with SMTP and hands over the message. At LJPc hosting that server is ljpc.email, on port 465 or 587.
2. The outgoing server looks up the MX record of the recipient's domain in DNS. MX stands for mail exchanger: the record names the mail server that accepts email for that domain. See what is an MX record for details.
3. The outgoing server delivers the message to that mail server with SMTP, over port 25. The receiving server checks things like SPF, DKIM and DMARC and places the message in the recipient's mailbox.
4. The recipient opens their email app, which fetches the message with IMAP or POP3.

Port 25 is for traffic between mail servers. In your own email app, you send through port 465 or 587 and sign in with your email address and password.

IMAP: the same mailbox on every device

With IMAP, your messages and folders stay on the server. Your email app shows them and keeps everything in sync: read a message on your phone and it shows as read on your laptop too. Move it to a folder and it is in that folder everywhere. Most email apps also keep sent messages and drafts in folders on the server, so you find them on every device and in LJPc webmail.

What else you get with IMAP:

• New mail right away. Our server supports IMAP IDLE: while your email app is connected, the server reports new messages immediately.
• Offline reading. Many email apps keep a copy on your device, so you can read messages that have already arrived without an internet connection.
• Your mail survives a lost or broken device. Everything is still on the server. Set up your address again and your mail is back.

Two things to keep in mind. Delete a message on one device and it is gone everywhere. And because your mail lives on the server, it counts towards the storage of your hosting package; check your storage usage explains how to see it.

POP3: download your mail to one device

POP3 works like emptying a mailbox. Your email app takes new messages from your inbox on the server and stores them on your device. Depending on the setting, it then deletes them from the server or leaves them there for a while.

POP3 only knows the inbox. Folders, read status and sent messages stay on the device where you created them. If you download with POP3 on two devices, neither one shows what you did on the other.

POP3 suits you if you deliberately keep your mail on one computer, for example as your own archive. Back that computer up: if it fails, mail that only lived there is gone. If you want POP3 to keep a copy on the server, turn that on in your email app; in Thunderbird the option is called Leave messages on server, as described in how to set up email in Thunderbird.

IMAP vs POP3 at a glance

Which protocol should you use?

• You read email on more than one device, or in webmail: use IMAP.
• You share a mailbox with colleagues, such as info@: use IMAP, so everyone sees which messages have been answered.
• You deliberately keep everything on one computer: POP3 works, with regular backups of that computer.
• Sending: always SMTP, on port 465 or 587.

Not sure? Choose IMAP. It is also what our email profile for iPhone and iPad sets up. Some email apps only support IMAP, such as Spark and Mailspring.

How to switch from POP3 to IMAP

Most email apps cannot convert an existing POP3 account to IMAP. Instead, you add your address again and bring your messages along:

1. Sign in to webmail and check which messages are still on the server.
2. Add your email address to your email app again and choose IMAP, using the settings further down this page.
3. Drag the messages and folders that only exist in your POP3 account into folders of the new IMAP account. Your email app copies them to the server.
4. Check in webmail that everything is there.
5. Only then remove the POP3 account from your email app. On an iPhone or iPad, follow how to remove an email account from your iPhone or iPad.

Got a lot of old mail? Check how much space is left in your hosting package first: everything you copy to the server counts towards your storage.

SMTP: how sending works

You use SMTP to send, whether you chose IMAP or POP3 for receiving. At LJPc hosting you choose between two ports in your email app:

• Port 465 with SSL/TLS: the connection is encrypted from the very first moment.
• Port 587 with STARTTLS: the connection starts unencrypted and switches to encryption before you sign in.

Both are secure when set up correctly. The internet standard RFC 8314 from 2018 prefers encryption from the start, which means port 465. If one port does not work, try the other. The outgoing server always asks you to sign in, with the same email address and password you use for incoming mail.

When you send through ljpc.email, your domain's SPF record must contain include:_spf.ljpc.network. If your hosting and DNS are with us, that entry is there by default. If another provider manages your DNS, add it there.

Moving to a new mail server, for example when you switch to LJPc, involves more than a new SMTP server: your mailboxes, your existing mail, the MX record and SPF all move with you. The full plan is in how to migrate email to a new server.

Modern alternatives: JMAP, Exchange and Microsoft Graph

IMAP, POP3 and SMTP are open standards that are not tied to any one provider: almost every email app supports IMAP and SMTP. Alongside them are newer protocols and protocols tied to one vendor.

JMAP, the successor to IMAP

JMAP (JSON Meta Application Protocol) was published by the IETF in 2019 as RFC 8620 and, for email, RFC 8621. It runs over HTTPS with JSON, like a modern app, and combines fetching, sending and push notifications in one protocol. It is designed to use network connections sparingly, which helps most on a phone.

JMAP comes from Fastmail, which uses it in its own apps, and server software such as Stalwart supports it. The mainstream email apps do not use it yet: Thunderbird is exploring it for its mobile apps and is still listed as requested on the JMAP software list. For now, IMAP remains the standard that works everywhere.

Exchange and Microsoft 365

Microsoft Exchange and Microsoft 365 use their own protocols. Phones and tablets connect with Exchange ActiveSync, and apps and integrations use Microsoft Graph. Besides email, they sync calendars and contacts. These are changing too: Microsoft began blocking the older Exchange Web Services (EWS) in Exchange Online on October 1, 2026, step by step, with Microsoft Graph as its replacement.

To host Exchange yourself, Microsoft offers Exchange Server Subscription Edition, available since July 1, 2025. Exchange Server 2016 and 2019 reached end of support on October 14, 2025. Running your own Exchange server takes Windows Server, licences and ongoing maintenance.

Webmail

Webmail is not a protocol for your email app but a website where you read your mail. Behind the scenes, webmail talks to the mail server with IMAP and SMTP, so you see the same folders as on your other devices. With LJPc hosting, webmail is at ljpc.email.

IMAP, POP3 and SMTP settings for LJPc hosting

For your email address with LJPc hosting, use these settings in any email app:

Always use these encrypted ports, so your password and messages travel encrypted between your device and our server. Step-by-step instructions per device are in set up your email on your phone, tablet and computer, and there are guides for Outlook, Apple Mail, Samsung Email and Gmail. The Gmail guide also lists Gmail's own IMAP and POP settings and what Google is changing about POP fetching.

What LJPc hosting takes care of

If your hosting and DNS are with us, the MX record, SPF, DKIM and DMARC are set up for you by default. For most domains on our nameservers, the details for automatic setup are in place too, so Outlook and Thunderbird often find the servers on their own. On iPhone and iPad, you set up your mail with our signed email profile, which chooses IMAP for you.

You create new email addresses and change passwords in the customer portal, as described in create an email address in the customer portal. If mail is not arriving or a message is stuck in your outbox, see how to fix email problems. Still stuck? Create a support ticket and we will gladly help.