use delivery in order to select correct contact_mechanism
https://discuss.tryton.org/t/party-sale-delivery-contact-mechanism/3671/7
#9991 (closed) added party.contact_mechanism,delivery usage.
Begin to use this in other modules. Candidates are:
stock_package_shipping
stock_package_shipping_dpd
stock_package_shipping_ups
notification modules (@ced)
For notification it may be also usefull for more modules like purchase, sale (@pokoli)