50.5 IMAP IDLE (Real-Time Notifications)
50.5.1 Overview ¶
IMAP IDLE ensures that the program reacts to new emails within a few seconds. Instead of polling the mailbox at regular intervals, the program keeps a connection open over which the server reports incoming emails immediately.
The program turns IDLE on automatically for every monitored folder, provided the server supports it (all common hosters) and the account option Use IDLE connection is enabled.
50.5.2 Activation ¶
In the account editor for IMAP accounts:
| Field |
Description |
| Use IDLE connection |
Turns IDLE on for this account. Default: on |
The option is decided per account - for individual accounts with server quirks, IDLE can be turned off selectively without affecting other accounts.
Note: Microsoft 365 and POP3 accounts do not show the option. Microsoft 365 uses its own real-time mechanism; POP3 does not support IDLE.
50.5.3 Latency ¶
With IDLE active, the typical latency from email arrival to start of processing is a few seconds. Without IDLE, the program waits for the next regular check cycle (see chapter 40.7) - depending on the interval, that can be several minutes.
50.5.4 Safety Net: Regular Check ¶
Even with IDLE active, the normal check interval continues to run - it serves as additional safety in case an IDLE notification is lost (e.g. due to a brief connection interruption). Both mechanisms complement each other so that no email goes unprocessed.
50.5.5 When IDLE Does Not Work ¶
| Situation |
Behavior |
| Server does not support IDLE |
Program falls back automatically to the normal check interval, no error |
| Firewall with short timeout |
IDLE connection drops regularly and is rebuilt. With very aggressive firewalls, disable IDLE |
| Folder is marked as “unreachable” |
IDLE does not start for this folder until it is reachable again (see chapter 50.6) |
50.5.6 Use Case ¶
Real-Time Auto-Reply
IMAP account with IDLE enabled and a profile with the task Reply. A customer inquiry is answered within a few seconds with an acknowledgement - the mailbox reacts noticeably faster than with pure check-interval polling.
50.5.7 Tip ¶
- A change to the IDLE option takes effect only after the processing is restarted (e.g. program or service restart)