Email protocols allow communication between email servers and email clients. Understanding the differences between the main protocols – SMTP, POP3 and IMAP – can help you choose the right setup.

Simple Mail Transfer Protocol (SMTP) is used for sending email from clients to servers. It doesn’t handle storage so isn’t suitable for accessing email from multiple devices.

Post Office Protocol version 3 (POP3) allows email clients to connect to servers and download messages for storage locally. Because the emails are then only stored locally, POP3 doesn’t support accessing the same inbox from multiple devices.

Internet Message Access Protocol (IMAP) permits access to email stored on a server from multiple devices. As the emails stay on the server rather than being downloaded, IMAP enables inbox synchronization across gadgets.


When to choose SMTP

Use SMTP for sending outbound emails via an email client. As a send-only protocol, key uses include:

  • Forwarding email from one address to another
  • Delivering email from sites/apps/devices to recipients

SMTP is built for transmitting rather than storing messages. It queues outbound emails until the next server is ready to receive them.

When to use POP3

The main situation for using POP3 is if you’ll only access email from one device. As a download-and-delete system, POP3 is ideal if you:

  • Don’t need to view emails across multiple gadgets
  • Have limited storage space on your email server
  • Prefer to store emails locally for organizing into folders

Bear in mind that any emails downloaded via POP3 and then deleted from the server won’t be accessible from other devices.

When to use IMAP

For accessing the same inbox from multiple gadgets, IMAP is the best fit. Key advantages include:

  • Emails remain on the server rather than being deleted after download
  • mailbox synchronization across devices
  • Remote access allows easy viewing when travelling
  • More reliable than POP3 for large attachments

The main downsides are potential storage limits on hosting plans and needing an internet connection to view messages.

Overall IMAP offers superior accessibility which is why most major email providers, including Gmail and, now use it by default rather than POP3.

Key Differences

Purpose Sending email Receiving email Receiving email
Storage Doesn’t store messages Downloads to local device Stored on email server
Number of devices No limit Single device recommended Multiple device access
Accessible when offline? No – requires connection for sending Yes – stores emails locally No – fetches emails from server

Key Takeaways

  • Use SMTP for sending outbound emails from an email client or app
  • Choose POP3 if you’ll only manage emails on one device
  • IMAP allows inbox synchronization across multiple gadgets
  • IMAP provides more convenience whereas POP3 may suit limited storage better

Understanding the contrasts between protocols aids selecting the ideal setup. An email provider’s default settings don’t necessarily match specific access preferences.


The differences between SMTP, POP3 and IMAP come down to the way emails are sent, stored and accessed. SMTP handles outgoing messages without storage. POP3 downloads emails to a single device. IMAP retains messages on the server for multi-device convenience.

Evaluating your usage patterns in terms of storage, syncing and accessibility determines the best protocol. While IMAP suits most users, POP3 remains relevant for low storage and one-device scenarios. Configuring SMTP is only necessary when setting up custom sending for newsletters, notifications or similar.

Comparing these systems allows tailoring an email workflow for ideal functioning across devices, servers and connections.

Frequently Asked Questions

What is SMTP commonly used for?

SMTP is most commonly used for sending outbound emails. Major uses include forwarding email from one address to another and delivering messages from websites, applications or services that generate notifications.

What are the disadvantages of POP3?

The main POP3 disadvantages are only being able to access email from one device, having emails deleted from the server after downloading them, and losing emails if they are deleted accidentally or due to device failure.

What are two benefits of using IMAP?

Two key IMAP benefits are accessing the same inbox from multiple devices and having emails stored in a central location on the email server, enabling viewing from anywhere with an internet connection.

Does Gmail use SMTP, POP3 or IMAP?

Gmail utilizes SMTP for sending email and IMAP for receiving messages. By default, Gmail uses IMAP which allows inbox syncing across devices.

Can you use POP3 and IMAP at the same time?

Most email services do not allow simultaneous connections over both POP3 and IMAP to the same account. Users typically have to select either POP3 or IMAP when configuring email software.

Is POP3 more secure than IMAP?

No, IMAP offers improved security over POP3. Encryption methods like SSL/TLS are supported by both protocols whereas IMAP has more evolved user authentication through AUTH LOGIN or AUTH XOAUTH.

How do webmail clients send email?

Webmail services utilize SMTP for outbound email transmissions just like standard email clients. The webmail interface communicates with the email server via SMTP to dispatch outgoing messages.

What port does SMTP use?

SMTP traffic commonly uses port 25 for unencrypted connections. For SMTP connections secured by SSL/TLS encryption, port 465 or port 587 is typically implemented.

Can SMTP servers store email?

No, SMTP servers are specialized for facilitating email transmission rather than storage. After forwarding messages to the next SMTP server, no copies are retained as storage takes place on POP3 or IMAP systems.

What is a POP3 server?

A POP3 server manages user mailboxes and allows POP3 email clients to connect for purposes like retrieving emails and marking messages as read or deleted. Examples include dedicated POP3 services or functions within multiprotocol mail servers.

How does IMAP differ from webmail?

Both IMAP and webmail allow multi-device access rather than downloading emails exclusively to one device like POP3 often does. However, IMAP requires specific client software while webmail offers mailbox access directly through a website.

Are messages downloaded via IMAP stored locally?

No, one of the defining IMAP characteristics is it does not download messages to local storage by default. IMAP stores all emails on the mail server to enable universal access unless a user alters settings to keep some emails exclusively on a specific device.

Which email providers support SMTP?

All major email services such as Gmail, Outlook, Yahoo Mail, iCloud Mail and FastMail implement SMTP for sending outbound messages. Web hosting packages also universally provide SMTP capability to let hosted email accounts dispatch messages.

What are the most common IMAP and POP3 ports?

For POP3, the standard ports are 110 (unencrypted traffic) and 995 (SSL/TLS encryption). With IMAP, the matching ports are 143 (unencrypted) and 993 (encrypted). Email providers and IT administrators may opt to implement non-standard ports too.

How many devices can access one IMAP account simultaneously?

Theoretically, there is no limit on concurrent IMAP connections for a single account. However, in practice email providers often enforce session limits to maintain performance, typically allowing 3-10 concurrent IMAP logins depending on the service.

Can SMTP send messages to multiple recipients?

Yes. In fact, sending messages to groups of recipients via features like CC and BCC is one of SMTP’s core capabilities. SMTP transmissions routinely dispatch copies of single emails to myriad recipients based on a message’s addressing information.

Does Microsoft 365 support POP3?

Yes, while Microsoft 365 utilizes IMAP by default, POP3 access can be optionally configured. The setting allows users to connect Microsoft 365 accounts to email software with only POP3 capabilities, if preferred over the standard IMAP functionality.

Can SMTP receive emails?

No, SMTP has no capacity for receiving or storing incoming messages. It is exclusively designed for dispatching emails to mail servers using the address info encoded into the message and attached server instructions to deliver the content.


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