[enhancement]: Supports the After-Queue Mode

[Boomboomdunce]

Which feature or improvement would you like to request?

Before using Stalwart, I was using a combination of Postfix and Fuglu in the after-queue mode. The main reason I chose this mode was that, regardless of how high the latency of the security detection program was (e.g., resource-intensive processes like antivirus scans or extracting compressed files), Postfix would always accept emails and not block the incoming queue. This ensured that the sender's experience would not be disrupted, and high concurrency would not block the sender's delivery attempts.

Now, I am using Stalwart's MTA-hook interface to integrate my own malicious detection program for email protection. However, when my malicious detection program reaches its performance limits, it blocks the sender's ability to continue delivering emails, thereby affecting the email service.

I hope that Stalwart can provide an output mechanism or a mode similar to Postfix's after-queue mode, allowing the security detection process to be placed in a post-queue stage so that it does not affect incoming email delivery operations.

Is your feature request related to a problem?

No response

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