Feature proposal: SMTP relay throttle, blockage and warning system

Jesper.Knudsen

New Member
Jan 4, 2024
1
0
1
Background:

If a client using the server as an outbound SMTP gets infected with some kind of spam bot, it is typically very hard for the spam filter to detect this and block e-mails. This means that this infected client can and will send many many e-mails out ultimately potentially resulting in the spam filters IP address or sending domain being blacklisted.

Feature proposal:

Create a limit of daily e-mails sent by a domain (domain specific threshold) that will prevent a massive overflow. This threshold can be a manually configured threshold or calculated based on historical volume. The easer is obviously just a manual threshold. A more detailed model would be to create threshold on a per e-mail sender pr. domain. When the threshold has been reached the system should no longer accept sending e-mails from this certain sender (SMTP 5xx code) until 24 hours have passed. Some kind of admin reset must be provided in the UI.

Another potential feature add-on to the above is to have an additional Buffer Pool of e-mails that can be used when the daily threshold has been reached – this will allow for a lower daily limit and provide room for legitimate mail blasts (newsletters, etc.).

On top of these threshold, the system should send warning e-mails to both the administrator and “violating” e-mail sender when a percentage of the daily threshold has been reached and also again when the threshold has been fully reached.
 

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