It returns something like "The mobilenumber "XXXXXX" contains invalid characters".
At what moment do you face the error? Please, provide all the steps you take before the error occurs. Also, please, specify what exactly you did in terms of configuration. Screenshots will be much appreciated. You can post them here or send us at firstname.lastname@example.org.
Is there a chance to "pre set" the standard front type in the configuartion to a specific front type and size for the exchange automatic reply when using the Adaxes?
Unfortunately, there is no such possibility.