If you set up a business email account on a hosting platform, in a control panel such as Plesk, or in an email client like Outlook, Apple Mail, or Thunderbird, you will usually see three protocol names: SMTP, IMAP, and POP3. These are not interchangeable. Each one has a specific role in sending, receiving, and synchronizing email.
Understanding the difference helps you configure mailboxes correctly, avoid connection errors, and choose the right settings for your devices. It also makes troubleshooting much easier when email is not sending, messages are missing, or a mailbox is not syncing across phone and desktop.
This guide explains what SMTP, IMAP, and POP3 do, how they work together, and which settings are usually recommended for hosted business email accounts.
What is SMTP?
SMTP stands for Simple Mail Transfer Protocol. It is the standard protocol used to send email from a client or mail server to another mail server.
When you click Send in your email client, SMTP is the protocol responsible for transferring the message out of your mailbox and toward the recipient’s mail server. It is also used for sending messages between mail servers on the internet.
What SMTP does
- Sends outbound email from your email client
- Transfers email between mail servers
- Supports authentication for outgoing mail on most hosting platforms
- Works together with port and security settings such as TLS or SSL
What SMTP does not do
- It does not download or synchronize incoming mail to your inbox
- It is not used for reading email
- It does not replace IMAP or POP3 for mailbox access
In a hosting environment, SMTP is usually configured with authentication. This means the email client must log in with a valid mailbox username and password before sending messages. This helps prevent unauthorized use of the mail server and improves deliverability.
What is IMAP?
IMAP stands for Internet Message Access Protocol. It is used to access and synchronize incoming email on the mail server without removing messages from the server by default.
IMAP is the preferred protocol for most modern email setups because it keeps your mailbox synchronized across multiple devices. If you read, delete, move, or mark messages on one device, those changes are reflected on other devices connected to the same mailbox.
What IMAP does
- Displays messages stored on the mail server
- Keeps folders and message status synchronized across devices
- Lets you access the same mailbox from phone, laptop, and webmail
- Supports server-side organization of email
Why IMAP is commonly recommended
For business email hosted on a control panel or managed hosting platform, IMAP is usually the best choice because it keeps the mailbox consistent everywhere. If you check mail on multiple devices or use webmail and an email client at the same time, IMAP prevents confusion and duplicate work.
With IMAP, your data remains on the server, so your inbox is easier to manage centrally. This is especially useful for shared mailboxes, support addresses, and teams that need to access the same account from different locations.
What is POP3?
POP3 stands for Post Office Protocol version 3. It is an older protocol used to download incoming email from the mail server to a local device.
POP3 was designed for a time when users typically checked email from a single computer. It downloads messages to the client and often removes them from the server after retrieval, depending on the client settings.
What POP3 does
- Downloads email from the server to one device
- Can reduce server storage usage if messages are deleted from the server
- Works for simple single-device email access
Limitations of POP3
- Does not synchronize changes across multiple devices
- Folder structure is limited compared to IMAP
- Messages may disappear from the server after download
- Can cause inconsistencies if you read mail from more than one device
POP3 is still supported by many hosting providers and email clients, but for most users it is no longer the best default choice. It can be useful in specific situations, such as when a user wants a local archive on one workstation and does not need server synchronization.
SMTP vs IMAP vs POP3: Quick comparison
| Protocol | Main purpose | Direction | Best use case |
|---|---|---|---|
| SMTP | Sends email | Outgoing | Sending messages from your email client or between servers |
| IMAP | Accesses and syncs email | Incoming | Using the same mailbox on multiple devices |
| POP3 | Downloads email | Incoming | Single-device access and local storage |
In simple terms:
- SMTP sends
- IMAP syncs
- POP3 downloads
How these protocols work together
When you use a typical email account on a hosting platform, the three protocols often work as a set:
- You compose an email in your client.
- SMTP sends the outgoing message to the mail server.
- The recipient’s server receives the message.
- IMAP or POP3 retrieves incoming messages for reading.
This is why an email account can have separate incoming and outgoing settings. A mailbox may use IMAP or POP3 for incoming mail and SMTP for outgoing mail. If either side is misconfigured, email can fail to send or new messages may not appear correctly.
Which protocol should you use?
Use IMAP if you need synchronization
Choose IMAP if you:
- Check email from multiple devices
- Use webmail and a desktop client
- Want folders and read/unread status to stay consistent
- Manage a business mailbox with ongoing access needs
Use POP3 only if you need local downloading
Choose POP3 if you:
- Prefer to keep email stored mainly on one device
- Need a local copy of messages for offline access or archival workflows
- Do not need synchronization across multiple devices
Use SMTP for sending in all cases
SMTP is the standard outgoing protocol. Regardless of whether you use IMAP or POP3 for incoming messages, your email client usually needs SMTP to send mail.
Typical email settings in a hosting environment
Exact values depend on the hosting provider, domain name, and control panel configuration, but the structure is usually the same. In many hosting environments, including Plesk-based setups, you will need the following:
Incoming mail server
- IMAP server: mail.yourdomain.com or a host provided by the provider
- POP3 server: mail.yourdomain.com or a host provided by the provider
- Username: full email address
- Password: mailbox password
Outgoing mail server
- SMTP server: mail.yourdomain.com or provider-specified hostname
- Username: full email address
- Password: mailbox password
- Authentication: enabled
Common ports and security
- SMTP: port 587 with STARTTLS is commonly recommended
- SMTP with SSL: port 465 is also widely used
- IMAP: port 993 with SSL/TLS
- POP3: port 995 with SSL/TLS
Use secure connections whenever possible. Unencrypted email traffic can expose credentials and message content on insecure networks.
SMTP authentication and why it matters
In modern hosting setups, SMTP authentication is important because it verifies that the person sending mail is allowed to use the mailbox. Without authentication, many mail servers will reject outbound messages or flag them as suspicious.
SMTP authentication helps with:
- Preventing unauthorized sending
- Reducing spam abuse
- Improving message acceptance by recipient servers
- Ensuring your client can send through the hosting provider’s mail server
If you can receive email but cannot send it, the issue is often related to SMTP authentication, an incorrect password, the wrong port, or disabled encryption settings.
How to choose the right settings in Outlook, Apple Mail, or Thunderbird
Most desktop and mobile clients ask for separate incoming and outgoing settings. When configuring a hosted mailbox, make sure you enter both correctly.
Recommended approach
- Enter the full email address and mailbox password.
- Choose IMAP unless you have a specific reason to use POP3.
- Set the outgoing server to SMTP.
- Enable SMTP authentication.
- Use SSL/TLS or STARTTLS if supported by your provider.
- Confirm that the ports match the provider’s documentation.
If you use a control panel like Plesk, the mail settings may also be visible in the mailbox configuration or in the domain’s email account details. Providers often offer predefined settings to make setup easier.
Common email problems caused by incorrect protocol settings
Email sends but does not arrive in inbox
This may indicate a delivery issue, spam filtering problem, or a DNS-related configuration issue such as missing SPF, DKIM, or DMARC records. It is not always a protocol problem, but SMTP is involved in sending the message.
Messages arrive on one device but not another
This often happens when one device uses POP3 and another uses IMAP, or when accounts are configured inconsistently. IMAP is usually the better solution if you want the same mailbox state everywhere.
Can receive mail but cannot send
This usually points to SMTP configuration issues such as:
- Incorrect SMTP server name
- Wrong port
- SMTP authentication not enabled
- Wrong username or password
- Encryption mismatch
Old messages disappear from the server
This is often caused by POP3 settings that remove mail after download. If you want messages to stay on the server, use IMAP or adjust POP3 options carefully.
Folder changes are not syncing
This is typically an IMAP-related issue, or the client may be connected in offline mode. Confirm that the account is set up as IMAP and that synchronization settings are enabled.
Best practices for business email hosting
For most hosted business email accounts, the following practices are recommended:
- Use IMAP for incoming mail
- Use SMTP with authentication for outgoing mail
- Enable SSL/TLS or STARTTLS
- Use the full email address as the username
- Keep mailbox passwords strong and unique
- Verify DNS records such as SPF, DKIM, and DMARC for better deliverability
- Avoid mixing POP3 and IMAP on the same mailbox unless you fully understand the impact
In managed hosting and control panel environments, these settings help keep email reliable across devices and reduce support issues caused by inconsistent configurations.
IMAP vs POP3 for teams and shared mailboxes
Teams often use shared email addresses such as info@, sales@, or support@. For these mailboxes, IMAP is generally more practical because multiple users may need access at the same time.
With IMAP, team members can:
- See the same inbox state
- Track which messages have been read
- Organize mail into folders consistently
- Use webmail and desktop email clients together
POP3 is usually less suitable for shared mailboxes because it does not provide smooth synchronization between users.
FAQ
Is SMTP used for receiving email?
No. SMTP is used for sending email. Incoming email is handled by IMAP or POP3.
What is the best protocol for most users?
IMAP is usually the best choice for most modern users because it syncs email across devices and keeps the mailbox consistent.
Can I use both IMAP and POP3 on the same account?
Some clients may allow it, but it is not recommended unless you have a specific reason. Mixing them can lead to missing messages, duplicate mail, or inconsistent folder states.
Why does my email client ask for SMTP and IMAP separately?
Because sending and receiving are handled by different protocols. SMTP manages outgoing mail, while IMAP manages incoming mail synchronization.
Do I need SMTP authentication?
Yes, in most hosted email setups. Authentication is required to send mail through the provider’s server and is important for security and deliverability.
Which ports should I use?
Common secure ports are SMTP 587 or 465, IMAP 993, and POP3 995. Always follow your hosting provider’s documentation if it specifies different values.
Is webmail using SMTP, IMAP, or POP3?
Webmail uses the server-side mailbox system and typically interacts with mail storage in a way similar to IMAP for reading messages and SMTP for sending them. You do not manually configure those protocols in the browser, but they are still part of the email infrastructure.
Why do I see sent messages on one device but not another?
This can happen if the client is not configured with IMAP, or if sent folder synchronization is disabled. Check that the account uses IMAP and that folder mapping is correct.
Conclusion
SMTP, IMAP, and POP3 each serve a different purpose in email communication. SMTP sends messages, IMAP synchronizes incoming mail across devices, and POP3 downloads mail to one device. For most business email accounts on a hosting platform or in a control panel such as Plesk, the recommended setup is IMAP for incoming mail and SMTP for outgoing mail, both with authentication and secure connections enabled.
If you are configuring a new mailbox or troubleshooting email issues, checking the protocol type, server name, port, username, password, and encryption settings is one of the fastest ways to solve the problem. Choosing the right protocol from the start helps ensure reliable, secure, and consistent email access across all your devices.