It is not possible to change the quotation introduction added when answering mail. Andre Klapper ak-47@gmx.net

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 Changing the "On date, person wrote:" string when replying

Advanced users can change this string.

Open the dconf-editor application.

Navigate to org.gnome.evolution.mail.

Enter the prefered quotation string as the value for the key composer-message-attribution.

You might need to install dconf-editor to perform these steps.