This code contains the unique identifier for each XML mass-mailing setup.
It is limited to 10 characters.
It also conditions the name of the XML tag that will be used as the root of the generated document.
Two values deserve a particular attention:
MAILBPR: This value corresponds to the standard setup proposed by default for mass-mailings of the type
BP (business partners).
MAILCCN: This value corresponds to the standard setup proposed by default for mass-mailings of the type
Contacts.
If these two mass-mailings are modified, all the regeneration of the standard setup will lead to a return
to the initial status of these two setups.