📅 Friday, 17 October 2025
🕐 10:00 PM
Incoming Queue—New incoming emails entering the MTA are initially placed in the incoming queue. A high count in the incoming queue indicates that the active queue is filled to capacity.
Active Queue—Emails from the incoming queue are moved to the active queue to be forwarded to multiple MTA hosts. The appliance can store 20,000 active emails by default. When the Email Security - Server appliance is deployed in inline mode, this queue can be filled to capacity if delivery problems are found with one or more domains.
Hold Queue—Emails are moved to the hold queue while they are being scanned by the Email Security - Server appliance.
Deferred Queue—Emails are moved to the deferred queue if they cannot be delivered to the next-hop destination IP address. For example, emails are placed in the deferred queue if the next-hop MTA host is shut down or an invalid IP address was configured. The Email Security - Server appliance tries to deliver these emails until the deferred queue timer expires.
Bounced Queue—Emails that time out of the deferred queue are moved to the bounced queue. The email messages remain in the bounced queue until the bounced queue timer expires. The bounced queue timer begins the moment the Email Security - Server appliance receives the email.
Maildrop Queue—Emails are moved into the maildrop queue when the Email Security - Server appliance is ready to send the email to the next-hop destination IP address. Emails remain in the maildrop queue until the pickup process scans the maildrop queue and sends the email to the cleanup process for delivery.
Incoming Queue—New incoming emails entering the MTA are initially placed in the incoming queue. A high count in the incoming queue indicates that the active queue is filled to capacity.
Active Queue—Emails from the incoming queue are moved to the active queue to be forwarded to multiple MTA hosts. The appliance can store 20,000 active emails by default. When the Email Security - Server appliance is deployed in inline mode, this queue can be filled to capacity if delivery problems are found with one or more domains.
Hold Queue—Emails are moved to the hold queue while they are being scanned by the Email Security - Server appliance.
Deferred Queue—Emails are moved to the deferred queue if they cannot be delivered to the next-hop destination IP address. For example, emails are placed in the deferred queue if the next-hop MTA host is shut down or an invalid IP address was configured. The Email Security - Server appliance tries to deliver these emails until the deferred queue timer expires.
Bounced Queue—Emails that time out of the deferred queue are moved to the bounced queue. The email messages remain in the bounced queue until the bounced queue timer expires. The bounced queue timer begins the moment the Email Security - Server appliance receives the email.
Maildrop Queue—Emails are moved into the maildrop queue when the Email Security - Server appliance is ready to send the email to the next-hop destination IP address. Emails remain in the maildrop queue until the pickup process scans the maildrop queue and sends the email to the cleanup process for delivery.