Feature Request: Simulate 550 Recipient address rejected: User unknown in relay recipient table errors

[PDunbarCGI]

For functional application testing purposes, it would be helpful to be able to simulate delivery failures that occur for specific addresses such as:
550 Recipient address rejected: User unknown in relay recipient table;

where mail sent to a local address not recognized by the MTA is rejected.

[andy250]

Related: #165
I am considering giving it a try and sending a PR. It should be fairly simple. One way to control this would be to recognized some special code/string in the subject (configurable in appsettings). E.g. if subject contains configured code (e.g. [SMTP_ERROR:xxx]) then return error xxx.

[rnwood]

Thanks for the interest. For this and auto relay rules I was considering embedding an expression/script language so it can be used in the config. Something like https://github.com/microsoft/ClearScript... but that might be too large. The reason for this is to that it's as flexible as possible without being limited by a DSL/schema that only lets you express certain conditions. Fiddler HTTP debugger uses this approach with Fiddler script and I think it works well.

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________________________________ From: andy250 ***@***.***> Sent: Tuesday, March 12, 2024 6:56:32 AM To: rnwood/smtp4dev ***@***.***> Cc: Subscribed ***@***.***> Subject: Re: [rnwood/smtp4dev] Feature Request: Simulate 550 Recipient address rejected: User unknown in relay recipient table errors (Issue #1265) Related: #165<#165> I am considering giving it a try and sending a PR. It should be fairly simple. One way to control this would be to recognized some special code/string in the subject (configurable in appsettings). E.g. if subject contains configured code (e.g. [SMTP_ERROR:xxx]) then return error xxx. — Reply to this email directly, view it on GitHub<#1265 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/AAKEGF63DAC3DZVQSD4WIO3YX2RKBAVCNFSM6AAAAABCP2KEE6VHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMYTSOJQHEYDKMRSGA>. You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[andy250]

Yes, scripting would be very nice. Requires more effort though and understanding of bigger part of the app. I can't invest that much into this project atm, sorry. A rigid config-approach could be good enough for a start also, until scripting is adopted. I'll start with a fork and see how it goes.

[rnwood]

Implemented. See RecipientValidationExpression in the settings file (and also in the settings dialog in the UI).