IMAP vs POP3 and SMTP: An Email Settings Guide
IMAP vs POP3: what IMAP, POP3 and SMTP do, email port settings (993, 995, 465, 587), setup in Outlook, Thunderbird and on phones, and common errors.
IMAP, POP3 and SMTP are the three protocols email programs and phones use to talk to an email server. IMAP and POP3 are for receiving email, and SMTP is for sending it. The "incoming server", "outgoing server" and port numbers you're asked for when adding a business account to Outlook, Thunderbird or your phone's mail app belong to these protocols.
In this guide we explain what the three protocols do, the difference between IMAP and POP3, the right port settings, setting up an account in popular email programs and common errors.
What do IMAP, POP3 and SMTP do?
- SMTP (Simple Mail Transfer Protocol): Used to send email. Your program hands the email you wrote to your provider's server over SMTP; the server then delivers it to the recipient's server, again over SMTP.
- IMAP (Internet Message Access Protocol): Emails stay on the server; your program reads them from the server. When you read an email on your phone, it also shows as read on your computer.
- POP3 (Post Office Protocol 3): Emails are downloaded from the server to your computer and are usually deleted from the server. The emails stay only on that device.
In short: the incoming server is IMAP or POP3, and the outgoing server is SMTP.
The difference between IMAP and POP3
| Feature | IMAP | POP3 |
|---|---|---|
| Where are emails kept? | On the server | On the device they were downloaded to |
| Multiple devices | All devices are synced | Each device sees a separate copy, or none at all |
| Folders | On the server, the same everywhere | Only on that device |
| Sent items | Visible on all devices | Only on the device they were sent from |
| If the device is lost or breaks | Emails are safe on the server | Without a backup, the emails are lost |
| Server quota | Used | Freed up if emails are downloaded and deleted |
Since most people today access their email from a phone, a computer and webmail, IMAP is the right choice. POP3 only makes sense in special cases, such as archive accounts that are accessed from a single computer and shouldn't take up space on the server.
Email port settings
| Protocol | Encrypted port (recommended) | Other port |
|---|---|---|
| IMAP | 993 (SSL/TLS) | 143 (STARTTLS) |
| POP3 | 995 (SSL/TLS) | 110 (STARTTLS) |
| SMTP | 465 (SSL/TLS) | 587 (STARTTLS) |
- SSL/TLS ports encrypt the connection from the very start.
- STARTTLS first opens a plain connection and then switches to encryption. If your program has a STARTTLS option, don't use an unencrypted connection.
- Port 25 is used to relay email between servers. Many internet providers block this port on home connections, so use 465 or 587 as the outgoing server port in email programs.
We explain what ports are and how they work in our What is a port? post.
What you need to set up an account
Whichever program you use, you'll need the following:
- Email address and password
- Username: Almost always the full email address (
name@yourdomain.com). - Incoming server (IMAP): The address your provider gives you, port
993, SSL/TLS. - Outgoing server (SMTP): The address your provider gives you, port
465(SSL/TLS) or587(STARTTLS). - Outgoing server authentication: On; the same username and password as the incoming server.
You can find the server addresses in your email provider's control panel or in the email containing your account details.
Setting up Outlook, Thunderbird and phones
Outlook: Go to File → Add Account, type your email address, check Let me set up my account manually under Advanced options and choose IMAP. Enter the incoming and outgoing server details as shown above.
Thunderbird: When adding an account, type your name, email address and password. Thunderbird tries to find the settings automatically; if it can't, or finds the wrong ones, enter the server details yourself with the Configure manually button.
iPhone and iPad: Go to Settings → Mail → Accounts → Add Account → Other → Add Mail Account. After entering your details, make sure the IMAP tab is selected and fill in the incoming and outgoing server details.
Android: In the Gmail app, use Add account → Other to type your email address, choose Personal (IMAP) as the account type and enter the server details.
Even when a program finds the settings automatically, checking the port and encryption settings prevents problems later.
Common email errors
- Authentication error: First check that you can log in to webmail with the same details. Make sure the username is the full email address. Too many failed attempts can get the account temporarily blocked.
- Email won't send: Set the outgoing server port to 465 or 587 and check that authentication is turned on for the outgoing server. Port 25 is blocked on many home connections.
- Certificate warning: The server name you entered in the program doesn't match the name on the server's SSL certificate. Use exactly the server name your provider recommends.
- Emails are on one device but not the other: One of the devices connects over POP3 and downloads and deletes emails from the server. Switch all devices to IMAP.
- Sent emails land in spam: This isn't a program setting; it's a domain setting. Check your SPF, DKIM and DMARC records; we explain these in our SPF, DKIM and DMARC explained post.
- Mailbox full: With IMAP, emails take up space on the server. Delete large attachments or archive old emails.
Email with Nodesty mail hosting
Nodesty mail hosting plans work with every email program and mobile device that supports IMAP and POP3; you can also access your email from the browser with webmail. Incoming email is filtered with SpamExperts, so spam and malicious emails are stopped before they reach your inbox. We explain how to create an email address on your own domain step by step in our How to create a business email address guide; you can also move your emails from another provider to your new account over IMAP.
Frequently Asked Questions
Should I use IMAP or POP3?
If you access your email from more than one device, use IMAP; read, deleted and moved emails are synced across all your devices. POP3 only suits cases where you use a single computer and don't want to keep emails on the server. Today, IMAP is the right choice for most users.
Where do I find my incoming and outgoing server addresses?
The server addresses are listed in your email provider's control panel or in the details sent when the account was created. It's usually an address like mail.yourdomain.com or the provider's own server name. Always enter the full email address as the username.
Should I use 465 or 587?
Both are for sending email securely. 465 encrypts the connection with SSL/TLS from the very start, while 587 first opens a plain connection and then switches to encryption with STARTTLS. Use the one your provider recommends; if both are supported, 465 usually causes fewer problems.
I can send email but can't receive it. Why?
Incoming email is routed according to your domain's MX record. If the MX record points to the wrong server, or if you changed it recently, your email may be going somewhere else. Also check whether your mailbox is full.
My phone keeps saying my password is wrong. What should I do?
First check that you can log in to webmail with the same password. If you can, delete the account on your phone and add it again, making sure the username is the full email address and that authentication is turned on for the outgoing server. Too many failed attempts can get your account temporarily blocked.
Can I move my Gmail emails to my new account?
Yes. You can add both the old and new account to the same email program over IMAP and drag the folders across, or move your emails with a tool like imapsync. Don't close the old account until the move is finished.
About the author
Nodesty Team · Infrastructure & Support
The Nodesty team runs our servers, network and DDoS protection day to day and answers customer support requests around the clock. These guides come from that work.
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