When importing work orders from a DMS, the e-mail adresses of customer from the DMS have priority over the e-mail addresses that are in Plan-IT. E-mail addresses from a DMS are always leading.
The e-mail address that is saved in Plan-IT is only used when you manually create a work order in Plan-IT without importing a work order from a DMS.
In the Plan-IT settings for CaRe-Mail, there are however 2 options that can give e-mail addresses from CaRe-Mail priority over the e-mail addresses from the DMS:

When 1 of these options is acivated, the e-mail addresses from CaRe-Mail are used instead of those from the DMS. Make sure to remove the checks from both of these options to make the e-mail addresses from the DMS leading.