Merging contacts re-sent segment emails (manual merge, redundant sending)

Your software
My Mautic version is: 4.1.2
My PHP version is: 7.4.33
My Database type and version is: mysql 8.0.33

Your problem
My problem is: Existing contacts clicked a link in a segment email, completed a form, and were assigned new IDs within Mautic. This resulted in duplicate contact IDs for the same person. (Emails were not collected in the form; perhaps that alone would solve this problem of duplication.)

Manually merging these contacts caused the original segment email to be sent to them again, as if a new contact were added to the segment.

I have a theory why this happened. When manually merging two contacts, the ID of the more recent contact will be used, with data ported over from older contact ID. Is that correct so far?

In that case, the new contact ID could appear as a newly added contact to the segment, if not caught as a merged contact by Mautic. Correct?

Then the question is: why the duplication in the first place?

The form in this case, did not collect email addresses. No email was sent to the form, and no form field was used to collect email address from the contact. I have a suspicion that using an email, even if sent by q param and retrieved by hidden field, it would eliminate the duplicate contact problem.

This last part, adding email to the form, I have not tested yet. I will have to report back on that.

I’d love to hear from anyone with experience on this particular aspect of Mautic.


Mautic out of the box uses email as the unique record identifier. You can change this in your settings if you prefer something esle be a UI.

So your theory is spot on.

I would recommend adding emails to every form you use. If the email is known you can set it to not be shown on the form, if Mautic’s tracking pixel is able to ID the contact. Our have an email field that is pre populated if known. That way the person does not have to fill it out, but can correct or update. Lastly you can set an email field but make it hidden so that mautic knows the form submission belongs to theta email field/contact.

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