II.4.2.10 The contractor must record and report to the contracting authority any problem that affects its ability  to provide the services. The report must describe the problem, state when it started and what action  the contractor is taking to resolve it.  II.5. COMMUNICATION BETWEEN THE PARTIES  II.5.1. Form and means of communication  Any communication of information, notices or documents under the FWC must:  (a) be made in writing in paper or electronic format in the language of the FWC; (b) bear the FWC number and, if applicable, the specific contract number;  (c) be made using the relevant communication details set out in Article I.8; and  (d) be sent by mail, e-mail or, for the documents specified in Annex XVII and under the conditions  specified therein, via e-PRIOR. If a party requests written confirmation of an e-mail within a reasonable time, the other party must provide an  original signed paper version of the communication as soon as possible.  The parties agree that any communication made by e-mail has full legal effect and is admissible as evidence  in judicial proceedings.  II.5.2. Date of communications by mail and e-mail  Any communication is deemed to have been made when the receiving party receives it, unless this FWC  refers to the date when the communication was sent.  E-mail is deemed to have been received by the receiving party on the day of dispatch of that e-mail, provided  that it is sent to the e-mail address indicated in Article I.8. The sending party must be able to prove the date  of dispatch. In the event that the sending party receives a non-delivery report, it must make every effort to  ensure that the other party actually receives the communication by e-mail or mail. In such a case, the  sending party is not held in breach of its obligation to send such communication within a specified deadline.  Mail sent to the contracting authority is deemed to have been received by the contracting authority on the  date on which the department responsible referred to in Article I.8 registers it. Formal notifications are considered to have been received by the receiving party on the date of receipt  indicated in the proof received by the sending party that the message was delivered to the specified  recipient.  II.5.3. Submission of e-documents via e-PRIOR  The exchange of electronic documents such as specific contracts and invoices between the parties may be  automated through the use of the e-PRIOR platform in accordance with the provisions of Annex XVII. This  platform provides two possibilities for such exchanges: either through web services (machine-to-machine  connection) or through a web application (the supplier portal).  If applicable, the contracting authority will take the necessary measures to implement and maintain electronic  systems that enable the supplier portal to be used effectively.  In the case of machine-to-machine connection, a direct connection is established between the parties’ back  offices. In this case, the parties take the measures necessary on their side to implement and maintain  electronic systems that enable the machine-to-machine connection to be used effectively. The electronic  systems are specified in the interface control document. The contractor (or leader in case of a joint tender)  must take the necessary technical measures to set up a machine-to-machine connection and at its own cost.  If communication via the supplier portal or via the web services (machine-to-machine connection) is hindered  by factors beyond the control of one party, it must notify the other immediately and the parties must take the  necessary measures to restore this communication.  18 