Enhancement Request: Optional Disable of SMTP Duplicate Message-ID Check

[1StreamInfra]

Background / Context

We use Odoo as a CRM platform for multiple customers. Odoo relies on IMAP to manage inbound and outbound email and uses Message-ID headers to track email conversations.

One of our clients is unable to use IMAP due to internal security policy. To work around this limitation, we successfully implemented DavMail as a middleware SMTP/IMAP connector. Overall, DavMail works reliably and has proven to be a solid solution in this environment.

Problem Description

Odoo sends emails to TO and CC recipients as separate SMTP messages while reusing the same Message-ID for tracking purposes.

From DavMail SMTP logs, we have observed that:

• The first message with a given Message-ID is accepted and sent successfully.
• Subsequent messages using the same Message-ID are dropped, as DavMail detects them as duplicates.
• This results in CC recipients not receiving emails, even though they were sent as distinct SMTP transactions.

This behaviour appears to be caused by the SMTP connector’s duplicate Message-ID protection logic.

Expected / Desired Behaviour

In some environments (such as CRM systems like Odoo), multiple emails with the same Message-ID are legitimate and intentional.

We would like the ability to:

• Disable or bypass Message-ID duplicate checking, or
• Make this behaviour configurable via a flag or setting

This would allow DavMail to forward all SMTP messages regardless of Message-ID reuse, leaving message tracking entirely to the client application.

Proposed Enhancement

• Introduce a configurable option (e.g. a flag or property) in the SMTP connector to:
• Enable or disable duplicate Message-ID checks

Default to the current behaviour to maintain backward compatibility

Additional Notes

If the duplicate suppression cannot be reliably addressed on the client side, this configuration option would greatly improve DavMail compatibility with CRM platforms and other systems that reuse Message-IDs by design.

We would be happy to test and provide feedback if such a feature is implemented.

[mguessan]

Introduced a new davmail.smtpAllowDuplicateSend parameter to allow multiple messages with same message id, can you please test with latest trunk build?

[1StreamInfra]

Thank you very much Mickael, I will get the new version in asap and let you know.

[franciscodavid]

Hi,

This is the same problem I described in #132

Have a look at franciscodavid@25698d1
It is not necessary to completely disable the check, only when the same Message-ID is found together with a different recipient list.

[esabol]

Have a look at franciscodavid@25698d1 It is not necessary to completely disable the check, only when the same Message-ID is found together with a different recipient list.

May I suggest submitting a PR based on the current master branch?