SMTP vs IMAP: What's the difference?
SMTP sends and relays email, while IMAP lets clients read and synchronize mail stored in a mailbox.
SMTP
SMTP is the protocol used to submit outgoing messages and relay mail between servers.
IMAP
IMAP is a mailbox access protocol used by clients to read, organize and synchronize messages stored on a mail server.
Key differences between SMTP and IMAP
| Decision factor | SMTP | IMAP |
|---|---|---|
| Direction | Submits and relays outgoing messages. | Retrieves and synchronizes mailbox content. |
| Typical endpoints | Mail clients to submission servers and mail servers to other mail servers. | Mail clients to mailbox servers. |
| State | Moves messages through the mail-delivery path. | Maintains user-visible mailbox folders, flags and message state. |
Choose SMTP if
Use SMTP for outbound mail submission and server-to-server message transport.
Choose IMAP if
Use IMAP when users need synchronized access to their mailbox from one or more devices.
Practical example
When a user clicks Send, the mail client submits the message to an SMTP service, which relays it toward the recipient domain. When the recipient opens their mail application, IMAP synchronizes the delivered message from the mailbox server. Both protocols participate in one user workflow but perform different jobs.
Can you use SMTP and IMAP together?
SMTP and IMAP are complementary and are commonly configured together in traditional mail clients. Cloud suites may expose additional proprietary or HTTPS-based APIs, but the underlying distinction remains useful: message transport is different from mailbox access.
Common mistake to avoid
If receiving mail works but sending fails, changing IMAP settings will not fix the SMTP path. Troubleshoot authentication, submission ports, TLS and relay policy separately. Likewise, an SMTP delivery success does not prove that an IMAP client is configured correctly.
Key takeaway
SMTP and IMAP are complementary: one handles sending, the other handles mailbox access.
Frequently asked questions
Can IMAP send email?
No. IMAP accesses a mailbox. Outgoing mail is normally submitted with SMTP or a provider-specific API.
Can SMTP read a mailbox?
No. SMTP transports messages; it does not provide normal folder and message synchronization for users.
Why do mail clients ask for two servers?
Because sending and mailbox access are separate functions and may use different hostnames, ports and authentication policies.