IMAP vs POP3: What's the Difference and Which to Use

IMAP (Internet Message Access Protocol) keeps your email on your provider's server and shows the same mailbox on every device you sign in from. POP3 (Post Office Protocol version 3), often just called POP, downloads messages to one device and usually deletes them from the server. The IMAP vs POP3 choice comes down to where your mail should live.

For a new phone or laptop, pick IMAP. If the app lists Microsoft 365 or Google as a choice, pick that instead.

The usual sign of POP3 is an inbox that differs between devices: emails opened on the office computer never reach your phone.

IMAP vs POP3 at a glance

IMAP and POP3 are two ways for an email app to collect mail from the server that received it. Neither one sends anything: outgoing mail is the job of SMTP, a separate protocol.

The IMAP vs POP3 difference is what happens to a message once your app has collected it (Microsoft Support).

What is IMAP?

IMAP is the standard that lets an email app work on a mailbox that stays with your provider. Your phone, laptop and webmail open the same copy, so a message you open or file on one shows as opened or filed on all.

Mail for your address first lands on your provider's server, the one your domain's MX (mail exchange) record points to. IMAP lets your app read and organise it there without taking it away.

The current version, IMAP4rev2, is RFC 9051, from August 2021, replacing RFC 3501 of 2003. An RFC (Request for Comments) is how the Internet Engineering Task Force publishes a standard.

An IMAP app downloads a message only when you open it, and leaves attachments until you ask for them, according to Microsoft Support. A phone stays quick even on a large mailbox.

With Gmail, spam is sorted on the server too. Google asks IMAP users to leave their app's own junk filter off, because Gmail filters spam before mail reaches the app (Gmail Help).

New mail can show up almost at once. With IDLE, an IMAP command, a waiting app asks the server to report new messages the moment they arrive, so it does not have to keep checking (RFC 9051, section 6.3.13).

What is POP3?

POP3 is an older standard that copies new mail down to one device. Its 1996 specification, RFC 1939, says that "normally, mail is downloaded and then deleted."

Most POP3 apps can be set to leave a copy on the server (Microsoft Learn). The messages stay there, but read status, folders and sent mail still stay on the device that handled them.

POP3 has no way to push new mail. The app signs in on a timer, and a server can set how often.

Gmail's POP3 server asks for at least 300 seconds between sign-ins. Under RFC 2449, the extension that defines this limit, an app set to check every minute can still sign in only once every five minutes.

Gmail's own help page describes POP3 as a one-computer setup, with downloads instead of real-time sync. For a second device, Gmail offers recent mode, which adds recent: in front of the address and reaches back only 30 days.

IMAP or POP3: which should you use?

For most people, POP3 vs IMAP is not a close call: use IMAP unless you want your mail kept on one machine and nowhere else. Microsoft 365 and Gmail accounts have a better route still, shown in the first two rows.

OAuth, which appears in those rows, is the sign-in where the app opens Google's or Microsoft's own login page. The app then holds a token, so your password is never stored in it.

Your setup	Choose	Why
Microsoft 365 work mailbox in Outlook	Add it as a Microsoft 365 account	Outlook connects to Microsoft 365 over Exchange, not IMAP
Gmail or Google Workspace on a phone	The Gmail app, or Sign in with Google in your mail app	Google's own help points you to Sign in with Google
Email from a web host or broadband provider, on several devices	IMAP	One mailbox that looks the same everywhere
One computer, a small mailbox allowance, no phone	POP3 can work	Downloading keeps the server under its limit
An archive you want off the server	POP3	Mail leaves the server by design

Exchange is Microsoft's own mailbox connection, and it also keeps your calendar and contacts in step. Microsoft says Outlook will not get OAuth for POP and IMAP on Microsoft 365; it connects over Exchange instead (Microsoft Learn).

Google is also ending one common use of POP3. Gmail's "Check emails from other accounts" pulls mail from another address into Gmail over POP3.

Since the end of March 2026, new users cannot turn it on; existing users keep it until January 2027 (Gmail Help). Google's replacements are forwarding from the other provider, or adding that account to the Gmail app, which connects over IMAP.

IMAP and POP3 settings in Gmail and Microsoft 365

Personal Gmail has IMAP permanently on, and almost everything else is a switch that you or your administrator controls. All four account types prefer a sign-in through Google or Microsoft to a saved password.

Account	IMAP	POP3	How apps sign in
Personal Gmail	Always on since January 2025, with no switch (Gmail Help)	Off until you pick an option under Settings > See all settings > Forwarding and POP/IMAP > POP download	Sign in with Google, or an app password as a fallback
Google Workspace	Turned on by an administrator in the Google Admin console, under Apps > Google Workspace > Gmail > End User Access; the admin can limit IMAP to OAuth apps	A separate box on the same page	OAuth, or an app password
Microsoft 365	On for each new mailbox, unless security defaults are on	Same as IMAP	OAuth only
Outlook.com	Off until you turn on Let devices and apps use IMAP under Settings > Mail > Forwarding and IMAP (Microsoft Support)	Let devices and apps use POP, on the same page	OAuth, which Microsoft calls Modern Auth

Since 14 March 2025, IMAP and POP on Google accounts no longer accept the ordinary account password (Google Workspace Admin Help). Gmail also allows up to 15 email apps on one account at a time (Gmail Help).

In Microsoft 365, an administrator changes either protocol per mailbox in the Exchange admin center. Go to Recipients > Mailboxes, select the mailbox, then Manage email apps settings on the General tab (Microsoft Learn).

Microsoft began switching off password sign-in for POP3 and IMAP in Exchange Online on 1 October 2022, and after 31 December 2022 no one could turn it back on (Microsoft Learn).

Provider	IMAP server	POP3 server
Gmail and Google Workspace	imap.gmail.com, port 993	pop.gmail.com, port 995
Microsoft 365 and Outlook.com	outlook.office365.com, port 993	outlook.office365.com, port 995

IMAP vs POP3 ports and encryption

Use port 993 for IMAP and 995 for POP3. On both, TLS (Transport Layer Security) encryption is in place before your app sends a single command, which is what the email standards now recommend.

Protocol	Port	Encryption	Use it when
IMAP	993	Implicit TLS, set up before any IMAP command	Your default; apps may still call this SSL, the name of TLS's predecessor
IMAP	143	STARTTLS: the app connects unencrypted and asks to upgrade	Your provider lists only this port
POP3	995	Implicit TLS	Your default for POP3
POP3	110	STLS (POP3's name for STARTTLS)	Your provider lists only this port

RFC 8314, from January 2018, recommends implicit TLS for both protocols. It also asks providers to phase out unencrypted access over time.

Gmail does not use the older ports at all. When we connected on 25 October 2026, imap.gmail.com and pop.gmail.com answered only on 993 and 995; 143 and 110 timed out. Microsoft's outlook.office365.com answered on all four.

Check which sign-in a mail server accepts

Before you blame a password, you can ask the server which sign-in methods it takes. Servers answer that question for anyone, signed in or not, so no account is involved.

On a Mac or Linux computer, the openssl tool opens the encrypted connection. Type the two short lines after it connects:

openssl s_client -connect outlook.office365.com:993 -servername outlook.office365.com -crlf -quiet
a1 capability
a2 logout

For POP3, connect to port 995 and send capa, then quit. IMAP names the sign-in methods after AUTH, and POP3 after SASL, short for Simple Authentication and Security Layer. PLAIN, like USER, takes a password, while XOAUTH2 and OAUTHBEARER are OAuth.

The lines that matter from Microsoft's and Gmail's answers on 25 October 2026:

outlook.office365.com, port 993 (IMAP)
* CAPABILITY IMAP4 IMAP4rev1 AUTH=XOAUTH2 LOGINDISABLED ... IDLE ...

imap.gmail.com, port 993 (IMAP)
* CAPABILITY IMAP4rev1 ... IDLE ... AUTH=XOAUTH2 AUTH=PLAIN AUTH=PLAIN-CLIENTTOKEN AUTH=OAUTHBEARER

outlook.office365.com, port 995 (POP3), after capa
SASL XOAUTH2

pop.gmail.com, port 995 (POP3), after capa
USER
LOGIN-DELAY 300
SASL PLAIN XOAUTH2 OAUTHBEARER

Both providers still announce IMAP4rev1, the 2003 version, and Microsoft lists XOAUTH2 alone, with LOGINDISABLED switching off IMAP's plain password command.

The outgoing server on the same settings screen is SMTP, which has ports of its own.

A MailGraf sending subdomain such as news.example.co.uk has no mailbox, so there is no IMAP account to add; replies go to the campaign's Reply-to address (Create a campaign).

Why your email app keeps asking for an IMAP password

The app asks again because the server refused the password it had saved. That happens for three reasons.

• You changed the account password. Google also cancels every app password at that moment (Google Account Help).
• The provider stopped taking passwords from apps. Remove the account from the device and add it back, so a current app signs in through the provider (Microsoft Learn).
• The app is too old for OAuth. Gmail Help names Outlook 2016 as an example of a client that may not support the sign-in it needs. Update the app, or move to one that offers Sign in with Google.

Is your IMAP password the same as your email password? With a mailbox from a web host or broadband provider, it usually is.

With Gmail, an app either opens Google's sign-in page or takes a 16-digit app password, which needs 2-Step Verification.

How to tell whether your email uses IMAP or POP3

The account settings in your mail app name the protocol. In classic Outlook for Windows, go to File > Account Settings > Account Settings, and the Email tab shows a Type for each account (Microsoft Support).

An Exchange account appears there as Microsoft Exchange. In any other app, the port is the surer sign: 995 or 110 means POP3, 993 or 143 means IMAP; Microsoft uses outlook.office365.com for both.

On an iPhone, Mail asks you to choose IMAP or POP only when it cannot find an account's settings by itself (Apple Support).

If a message is missing on every device, webmail included, the protocol is not to blame. The email may never have arrived, and the sender will usually get a bounce that says why.

How to switch from POP3 to IMAP without losing old emails

The safe order is back up first, connect over IMAP second and remove the old account last. Mail that POP3 has already taken off the server exists only on that computer, so it has to go back up to the server.

1. Check what the server still holds. Open webmail and compare it with the computer. Anything missing online is stored only on the POP3 computer.
2. Back up that computer's mail. In classic Outlook, go to File > Open & Export > Import/Export, choose Export to a file, then Outlook Data File (.pst) (Microsoft Support).
3. Stop the old account collecting mail, so it cannot pull new messages off the server during the move. In Thunderbird, untick both "Check for new messages" options in Server settings.
4. Add the same address again as a new account, and choose IMAP. For Gmail or Microsoft 365, pick Google or Microsoft 365 from the app's list instead.
5. Drag the old folders across into the IMAP account. They upload to the server, which can take a while for a large mailbox.
6. Check the folders on your phone or in webmail, then remove the POP3 account. Thunderbird warns that this cannot easily be undone.

If your mailbox allowance is small, keep the oldest mail in a local folder on the computer instead, as Thunderbird's help suggests. The phone will not show those messages, but the server keeps its room for new mail.