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A beginner-friendly guide to IMAP, POP3 and SMTP, explaining how email receiving and sending works across computers, phones and mail apps.
IMAP, POP3 and SMTP are email protocols. They are the rules your email app uses to receive, sync and send messages. If you have ever set up business email on Outlook, Apple Mail, Thunderbird, a phone or a tablet, you may have seen these terms in the account settings.
These settings can look confusing at first, but the basic idea is simple. IMAP and POP3 are used for receiving email. SMTP is used for sending email. Most modern business email setups use IMAP for incoming mail and SMTP for outgoing mail.
This guide explains what IMAP, POP3 and SMTP mean, how they work, which one you should use, and what to check if your business email is not sending or receiving properly.
IMAP keeps your email synced across devices, POP3 downloads email to one device, and SMTP sends outgoing email. For most modern business email users, IMAP plus SMTP is the best setup because it lets you access the same inbox from your computer, phone, tablet and webmail.
IMAP receives and syncs. POP3 receives and downloads. SMTP sends.
IMAP, POP3 and SMTP are email communication protocols. They help your email app talk to the mail server. Without them, your app would not know how to collect new messages, keep folders updated or send outgoing emails.
When you add an email account to a device, the app usually asks for incoming and outgoing server settings. The incoming server uses IMAP or POP3. The outgoing server uses SMTP.
If you use professional email with your own domain, such as hello@yourbusiness.co.uk, these settings allow you to connect that mailbox to the email app you prefer. If you need domain-based email, see our Business Email Hosting page.
| Protocol | What it does | Common use |
|---|---|---|
| IMAP | Receives email and keeps mail synced on the server. | Using the same mailbox on phone, laptop, tablet and webmail. |
| POP3 | Receives email by downloading messages to a device. | Older setups or single-device email use. |
| SMTP | Sends outgoing email from your mailbox. | Sending replies, quotes, invoices and customer messages. |
IMAP stands for Internet Message Access Protocol. It is used to receive email while keeping messages stored on the mail server. This means your inbox, sent items, folders and read status can stay synced across different devices.
For example, if you read an email on your phone, it can also show as read on your laptop. If you move a message into a folder in webmail, the same folder change can appear in your desktop email app. This makes IMAP ideal for modern business email.
IMAP is usually the best choice if you use more than one device, work from different locations, want access through webmail, or need your email history available wherever you log in.
POP3 stands for Post Office Protocol version 3. It is an older way of receiving email. POP3 usually downloads messages from the mail server to one device. Depending on settings, messages may then be removed from the server.
POP3 can still work, but it is less suitable for most modern users because it does not sync mail in the same way as IMAP. If you download mail to one computer using POP3, that same message may not appear properly on your phone, tablet or webmail.
POP3 may still be used in specific situations, such as older systems, single-device setups or users who intentionally want to download and store mail locally. For most business users, IMAP is usually the better choice.
Be careful when using POP3. Some setups remove messages from the server after downloading them. This can make email harder to access from other devices and can cause confusion if the device storing the mail fails.
SMTP stands for Simple Mail Transfer Protocol. It is used to send outgoing email. When you click send in your email app, SMTP is the protocol that passes the message to the outgoing mail server so it can be delivered to the recipient.
SMTP is needed whether you receive mail using IMAP or POP3. In other words, IMAP and POP3 are for incoming mail, while SMTP is for outgoing mail.
If you can receive emails but cannot send them, the issue is often related to SMTP settings. This may include the wrong outgoing server, wrong port, missing authentication, incorrect password or blocked connection.
IMAP or POP3 brings messages into your email app.
SMTP sends messages from your email app.
Your email app usually needs a username and password for SMTP sending.
For most people, IMAP is the better choice. It is designed for the way email is used today, with multiple devices, webmail access, synced folders and mobile working.
POP3 can still be useful in limited cases, but it is less flexible. It is more likely to cause confusion if you use several devices because messages may be downloaded to one device rather than staying properly synced on the server.
If you are setting up professional business email for a small business, use IMAP unless you have a specific reason to use POP3.
| Feature | IMAP | POP3 |
|---|---|---|
| Best for | Modern email use across multiple devices. | Older or single-device setups. |
| Where mail is stored | Mainly on the mail server. | Usually downloaded to the device. |
| Folder syncing | Yes, folders usually sync between devices. | Limited or no full folder syncing. |
| Webmail access | Works well with webmail. | May be incomplete if messages were downloaded and removed. |
| Storage usage | Uses server mailbox storage. | Can reduce server storage if mail is removed after download. |
| Recommended for business email | Usually yes. | Only for specific needs. |
When setting up email, your provider will usually give you incoming and outgoing server settings. These settings tell your email app how to connect to the mailbox.
You may see server names, ports, encryption methods, usernames and passwords. The exact details depend on your email hosting provider, so always use the settings provided for your specific mailbox.
Most business email setups use the full email address as the username. For example, if your mailbox is hello@yourbusiness.co.uk, the username is often the full address rather than just hello.
| Setting | What it means | Why it matters |
|---|---|---|
| Incoming server | The server used for IMAP or POP3. | Controls how your app receives mail. |
| Outgoing server | The server used for SMTP. | Controls how your app sends mail. |
| Port | The connection number used by the protocol. | The wrong port can stop connection working. |
| Encryption | SSL, TLS or STARTTLS security for the connection. | Helps protect login details and mail traffic. |
| Username | The account login, often the full email address. | Needed so the server knows which mailbox to access. |
| Password | The mailbox password or app password. | Needed for authentication. |
Email ports are connection numbers used by email protocols. Your email provider should tell you which ports to use. The table below shows common examples, but your exact setup may vary.
| Protocol | Common secure port | Purpose |
|---|---|---|
| IMAP | 993 | Receiving and syncing email securely. |
| POP3 | 995 | Downloading email securely. |
| SMTP | 465 or 587 | Sending email securely. |
SMTP authentication proves that you are allowed to send email through the outgoing mail server. Without authentication, mail servers could be abused to send spam. That is why most modern email services require a username and password before allowing messages to be sent.
If SMTP authentication is not enabled in your email app, you may receive messages but fail to send. This is one of the most common setup mistakes.
If your app asks whether the outgoing server requires authentication, the answer is usually yes. In many cases, it should use the same username and password as the incoming mailbox.
IMAP is useful because it keeps your mailbox on the server. Your phone, laptop, tablet and webmail all connect to the same mailbox. This means your folders and messages can stay consistent across devices.
If you send an email from your laptop, it can appear in the sent folder on your phone. If you move an email into a folder on webmail, that change can appear in your email app. This makes IMAP much easier for business users who work from several devices.
The main thing to remember is that deleting a message using IMAP may delete it from the server, which means it can disappear from other devices too. This is normal, but it is important to understand.
POP3 is less common for modern business email, but it can still be useful in specific cases. Some users prefer downloading messages to one device and keeping local archives. Some older systems may only support POP3. Some setups use POP3 to reduce server mailbox storage.
However, POP3 can cause problems if it is used without understanding the settings. If messages are removed from the server after download, they may not appear in webmail or on other devices. This can make troubleshooting difficult.
If you are unsure, choose IMAP instead of POP3 for normal business email.
SMTP handles outgoing mail. When you click send, your email app connects to the SMTP server, authenticates with your account details, then passes the message to be delivered.
The SMTP server may check whether your account is allowed to send, whether the message appears suspicious, whether the sender address matches the account, and whether the recipient can be reached.
If sending fails, check the SMTP server name, port, encryption, username, password and authentication settings. Also check whether your internet provider, firewall or email app is blocking the connection.
IMAP, POP3 and SMTP are email connection protocols, but DNS records are also important for email. DNS tells the internet where email for your domain should be delivered and which servers are allowed to send on its behalf.
MX records control where incoming email goes. SPF, DKIM and DMARC records help with sending trust and authentication. These records do not replace IMAP, POP3 or SMTP, but they work alongside them.
If you are setting up professional email, you can use our DNS Lookup tool to inspect records and our DNS Propagation Checker after making DNS changes.
Tell the internet where to deliver email for your domain.
Help receiving servers trust mail sent from your domain.
Let your email app receive, sync, download and send mail.
Imagine a small business creates the address hello@yourbusiness.co.uk. To use it properly, the domain needs email hosting, the mailbox needs to exist, DNS records need to point mail to the correct provider, and the user needs the right IMAP and SMTP settings in their email app.
On a laptop, the incoming server might use IMAP so the inbox stays synced. On a phone, the same IMAP settings can be used so the same mailbox appears there too. When sending from either device, SMTP handles outgoing mail.
This setup lets the business reply from the same professional email address whether they are at a desk, on mobile or using webmail.
Email setup problems are often caused by small mistakes in server settings. A wrong port number, missing authentication option or incorrect password can stop sending or receiving.
Another common issue is mixing IMAP and POP3 across devices. For example, one computer may download messages using POP3 and remove them from the server, while a phone using IMAP appears to have missing emails.
DNS mistakes can also cause problems. If MX records are wrong, new mail may not arrive. If SPF, DKIM or DMARC records are missing or incorrect, outgoing messages may be treated with less trust.
If incoming mail works but outgoing mail fails, the problem is usually related to SMTP. Check the outgoing server, port, encryption and authentication settings.
Make sure your email app is not trying to send without logging in. Most SMTP servers require authentication. Also check whether the sender address matches the mailbox you are using.
If SMTP settings look correct but sending still fails, try webmail. If webmail sends successfully, the problem is likely with the email app settings rather than the mailbox itself.
If sending works but messages do not arrive, check the incoming settings and DNS records. The email app may have the wrong IMAP or POP3 server, wrong port, wrong encryption setting or incorrect password.
If no messages arrive at all, MX records may be wrong. MX records tell the internet where to deliver email for your domain. If they point to the wrong provider, mail may not reach your mailbox.
Use DNS Lookup to check MX records and webmail to confirm whether the mailbox is receiving messages directly.
Email accounts often contain customer messages, invoices, passwords resets, quotes, attachments and private business information. Secure setup matters.
Use secure ports and encryption where available. Use strong passwords, avoid sharing mailbox logins, and enable two-factor authentication if your email platform supports it. Be careful when adding accounts to shared or public devices.
If a team needs access to email, consider separate accounts or properly managed shared mailboxes instead of one shared password.
A local business owner may want the same inbox on their phone, laptop and webmail. IMAP is the right choice because it keeps the mailbox synced. Messages read on the phone also show as read on the laptop.
SMTP is used for sending from both devices. If the owner replies to a customer from the phone, the sent message can also appear in the sent folder on the laptop if everything is configured correctly.
A business may have an old office computer using POP3. That computer downloads mail and removes it from the server. The owner then checks webmail or their phone and notices messages are missing.
In this case, the issue may not be the mail server. It may be the POP3 account settings. Moving to IMAP across all devices usually creates a cleaner modern setup.
A consultant sets up name@business.co.uk on a phone. Incoming mail works, but outgoing mail fails. The likely cause is SMTP settings, such as missing authentication or the wrong outgoing port.
Checking the SMTP server, secure port, username, password and authentication option usually fixes this type of issue.
IMAP is an incoming email protocol that keeps messages stored on the server and synced across devices. It is usually best for modern email users.
POP3 is an incoming email protocol that downloads messages to a device. It is older and less suitable for users who check email on several devices.
SMTP is the outgoing email protocol used to send messages from your email app through the mail server.
Most users should use IMAP because it syncs email across devices. POP3 is only better for specific older or single-device setups.
This is usually an SMTP issue. Check the outgoing server name, port, encryption, username, password and authentication settings.
Check your incoming IMAP or POP3 settings and your domain’s MX records. If MX records are wrong, mail may not reach your mailbox.
If you want an address such as hello@yourbusiness.co.uk, start with our Business Email Hosting options.
Need a domain first? Visit our Domain Services. If you are setting up a full website too, compare UK Web Hosting or visit Start Here.
You can also use our free DNS Lookup and DNS Propagation Checker tools when checking email DNS records.
IMAP, POP3 and SMTP are the basic protocols that help email apps receive, sync, download and send messages. IMAP and POP3 handle incoming email, while SMTP handles outgoing email.
For most modern business email users, IMAP and SMTP are the best combination. IMAP keeps your inbox synced across devices, and SMTP allows you to send from your professional email address.
If email setup goes wrong, check the basics first: server names, ports, encryption, usernames, passwords, SMTP authentication and DNS records. Most sending and receiving problems come down to one of those settings.
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