When setting up an email account in applications like Apollo, Outlook, or Apple Mail, you often encounter abbreviations such as IMAP, POP, and SMTP. These may seem like technical jargon, but they are essentially the “rules of communication” between your email client and the email server.
This article aims to help you understand the differences and functions of these three email protocols.
IMAP(Internet Message Access Protocol)
Keywords: Multi-device sync, Online viewing
IMAP is a protocol used for receiving emails, but it doesn’t download the emails directly to your local device. Instead, the emails remain stored on the mail server. The emails you see on your phone, computer, or tablet are actually synced copies residing on the server.
Advantages:
Supports multi-device sync. For example, if you delete an email on your phone, it will be automatically synced and deleted on your computer too.
Email content stays on the server, protecting against local data loss.
Disadvantages:
Occupies server storage space. If the mailbox storage is limited, regular cleanup is needed.
Typical Uses:
Modern email services like Gmail, enterprise email systems, and Outlook typically use IMAP mode for receiving emails by default.
POP3(Post Office Protocol v3)
Keywords: One-time download, Local storage
POP3 is also a protocol for receiving emails, but it works quite differently: It downloads emails directly to your local device and then deletes them from the server (though this can be set to be retained).
Advantages:
Emails are stored locally, freeing up server space.
Downloaded emails can be viewed without an internet connection.
Disadvantages:
Does not support multi-device sync. An email viewed on your phone might be completely unavailable on your computer.
If your device fails or you don’t have backups, emails can be lost.
Typical Uses:
Suitable for users managing email on a single device, or for scenarios with extreme storage requirements.
SMTP(Simple Mail Transfer Protocol)
Keywords: Sending emails
Regardless of whether you use IMAP or POP3, sending emails relies entirely on SMTP. It is the sole protocol used for dispatching emails. When you click the “Send” button, you’re essentially instructing SMTP to deliver your email from your computer to the recipient’s mail server.
Characteristics:
• All email clients (e.g., Apollo, Outlook, Apple Mail) require SMTP configuration to send messages.
• SMTP typically requires authentication (username + password) to authorize email dispatch.
The Difference Between IMAP, POP3 and SMTP
| Protocol | Purpose | Working Method | Stored on Server? |
|---|---|---|---|
| IMAP | Receiving | Viewing in sync | Yes |
| POP3 | Receiving | Read after download | No |
| SMTP | Sending | Mail delivery courier | N/A |
When do you need to know this?
If you’re configuring an email marketing tool like Apollo, or using an email client (Outlook, mobile email app) to send/receive company emails, you’ll need to provide these settings:
IMAP Host / Port (for incoming mail)
SMTP Host / Port (for outgoing mail)
These settings vary by email provider. Common configurations include:
| IMAP Host | SMTP Host | IMAP Port | SMTP Port | |
|---|---|---|---|---|
| Alibaba Cloud | imap.qiye.aliyun.com | smtp.qiye.aliyun.com | 993 | 465 |
| Tencent Enterprise Mailbox | imap.exmail.qq.com | smtp.exmail.qq.com | 993 | 465 / 587 |
| Gmail | imap.gmail.com | smtp.gmail.com | 993 | 465 / 587 |
| Outlook | outlook.office365.com | smtp.office365.com | 993 | 587 |
You just need to go to the official website of your email service provider to find the corresponding settings and fill them in.
Summary: Just remember three sentences
1.IMAP receives emails for “viewing in sync online”
2.POP3 receives emails but “downloads them locally”
3.SMTP is the essential “delivery protocol” for sending emails
Once you understand the division of labor and differences between these three, configuring email settings won’t confuse you anymore.
