Internet Message Access Protocol allowing clients to access and manage server-stored email messages
IMAP (Internet Message Access Protocol)
- Email retrieval protocol that allows clients to access and manage messages stored on a mail server
- Server-centric approach - emails remain on the server rather than being downloaded to local device
- Operates on TCP port 143 (unencrypted) and TCP port 993 (IMAP over SSL/TLS)
- Designed for users who access email from multiple devices or locations
Key Features and Functionality
- Multi-device synchronization - changes made on one device reflect across all connected clients
- Selective downloading - clients can download message headers first, then retrieve full messages on demand
- Server-side folder management - create, delete, and organize folders directly on the mail server
- Partial message retrieval - download only specific parts of messages
- Search capabilities - perform server-side searches without downloading all messages
IMAP vs POP3 Comparison
| Feature |
IMAP |
POP3 |
| Message Storage |
Server-side |
Client-side |
| Multi-device Access |
Full synchronization |
Limited |
| Bandwidth Usage |
Efficient |
Higher |
| Server Storage |
Requires more space |
Minimal |
| Offline Access |
Limited |
Full access |
| Ports |
143 (plain), 993 (SSL) |
110 (plain), 995 (SSL) |
Vocabulary
- Mailbox - Server-side container for messages
- UID - Unique Identifier assigned to each message
- IDLE - IMAP extension allowing real-time notifications
- Message flags - Status indicators (read/unread, deleted, flagged)
Notes
- Best for mobile users - server-centric approach ideal for multiple devices
- Storage planning - Organizations need significantly more server storage than POP3
- Configuration tip - Most modern email clients default to IMAP