Question
What does the "Possible Delivery" feature do?
Answer
When the Possible Delivery feature is enabled, AsyncOS treats any message as a "possible delivery" if it times out after the body of the message is delivered, but before the recipient host acknowledges receipt of the message. This functionality prevents recipients from receiving multiple copies of a message if continuous errors at their recipient host prevent acknowledgement of receipt. AsyncOS logs this recipient as a possible delivery in the mail logs and counts the message as completed.
myesa.local> deliveryconfig
Default interface to deliver mail: Auto
"Possible Delivery": Enabled
Default system wide maximum outbound message delivery
concurrency: 10000
Default system wide TLS maximum outbound message delivery
concurrency: 100
Choose the operation you want to perform:
- SETUP - Configure mail delivery.
[]> setup
Choose the default interface to deliver mail.
1. Auto
2. Management (192.168.0.199/24: myesa.local)
[1]>
Enable "Possible Delivery" (recommended)? [Y]>
Please enter the default system wide maximum outbound message
delivery concurrency.
[10000]>
Please enter the default system wide TLS maximum outbound message
delivery concurrency.
[100]>
The timeout is a TCP timeout, normally 5 minutes. SMTP will timeout before 4 minutes.
If this feature is disabled, the Email Security Appliance (ESA) will try to resend the message. If the feature is enabled, the message is seen as delivered.
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