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.
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) >
Enable "Possible Delivery" (recommended)? [Y]>
Please enter the default system wide maximum outbound message delivery concurrency. >
Please enter the default system wide TLS maximum outbound message delivery concurrency. >
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.