Definition
IMAP is the protocol defined in RFC 3501 (IMAP4rev1) for accessing a mailbox held on a server. Unlike a download-and-delete model, the server is the source of truth: a client fetches headers and bodies on demand, and any change it makes, such as marking a message read or moving it to a folder, is made on the server and seen by every other client.
Why it matters
Almost everyone reads mail on more than one device. With IMAP the phone, the laptop and webmail agree; with POP3 they diverge. IMAP also keeps the mailbox safe on the server if a laptop is lost, and it makes migration between providers a straightforward copy.
How it works
- The client opens a TLS connection to the server and logs in.
- It selects a folder and asks for the list of messages, receiving headers and flags first.
- Bodies and attachments are fetched when opened, or in the background for offline use.
- Actions (read, flag, move, delete) are sent as commands; the server applies them and reports the new state to any other connected client.
On ontechmail the IMAP server reads the same PostgreSQL mailbox that webmail, the OMail app and the REST API use, so there is no synchronisation step between them at all.
IMAP versus POP3
| IMAP | POP3 | |
|---|---|---|
| Where mail lives | On the server | Downloaded to one device |
| Multiple devices | All in sync | Each sees a different state |
| Folders and flags | Shared | Local only |
| ontechmail port | 993 (TLS) | 995 (TLS) |
| Use when | Always, unless a tool requires POP3 | Gmail's fetch-mail, legacy tools |
Example: ontechmail settings
| Setting | Incoming (IMAP) | Outgoing (SMTP) |
|---|---|---|
| Server | mail.ontech.co.zm | mail.ontech.co.zm |
| Port | 993 | 465 (SSL/TLS) or 587 (STARTTLS) |
| Encryption | SSL/TLS | SSL/TLS or STARTTLS |
| Username | your full email address | your full email address |
| Password | your mailbox password | same as incoming |
Outlook, Apple Mail and Thunderbird can usually discover these automatically, because ontechmail publishes autoconfig and autodiscover records. Signed-in users also get an Apple configuration profile from the dashboard's mail setup page.
Common problems
- "Cannot verify server identity." The client is using port 143 without TLS or the wrong hostname. Use mail.ontech.co.zm on 993.
- Login rejected. The username must be the full address, not the part before the @. If two-factor authentication is enabled, use your normal password; 2FA applies to webmail sign-in.
- Folders missing in a client. Subscribe to folders in the client's folder settings; some clients hide unsubscribed folders.
- Slow first sync. A large mailbox downloads headers for every folder on first run; subsequent syncs are incremental.
IMAP on ontechmail
The IMAP server is part of the platform rather than a bolted-on component, which is why state is instantly consistent across clients. It covers the operations everyday clients use: folder listing and creation, search, flags, move and copy, idle for push-style updates and append for saving drafts. If you need a specific extension for a migration tool, ask info@ontech.co.zm.
Frequently asked questions
What is IMAP?
IMAP, the Internet Message Access Protocol, lets a mail client read and manage messages that stay stored on the server. Folders, read state and flags are shared, so the same mailbox looks identical in webmail, on a laptop and on a phone.
What is the difference between IMAP and POP3?
POP3 downloads messages to one device and usually deletes them from the server; IMAP leaves them on the server and synchronises state across every client. IMAP is the right choice for anyone using more than one device.
What are the ontechmail IMAP settings?
Server mail.ontech.co.zm, port 993 with SSL/TLS, username is your full email address, and your mailbox password. Outgoing mail uses SMTP on port 465 (SSL) or 587 (STARTTLS) with the same credentials.
Does ontechmail support POP3 as well?
Yes. POP3 over TLS is available on port 995 for clients such as Gmail's fetch-mail feature that require it.