Attachment in third email

Have you added the file upload’s mail tag to the File attachments field in the “Mail (3)” section? Is it entered correctly? Each “Mail” that should have attached uploads needs the corresponding mail tag(s).

I did an upload on my test form after adding a new file mail tag to the form and both “Mail” and “Mail (3)”, and the messages had the correct upload attached.

In email 1 and email 2 is working ok “[documento-allegato][cf-allegato][visura-allegato]”. in email 3 is not.

Does the third email arrive missing the attachments? Or does it completely fail to arrive?

Yes. Just missing attachments, body text is working fine.

I have run more tests on my install and have been unable to make it fail. It may be a fault in my plugin but I can’t find it. Do you have any other plugins that interact with CF7 in any way?

Try creating a new test form with only a single file upload control, and add it to a new private page. You can use that to submit it without it being visible to the public. Set the To addresses to some other emails, and/or use test services like Mail dash Tester dot com. If the new form works, then it is an error with the other form.

If attachments are lost for every form, regardless of settings, the only option is to have a developer you trust debug the whole send process of the test form with Xdebug, or some conditionally-executed var_dump statements.