Purchase Order not sent to Supplier via email using B2B email delivery method

Summary:

Hi Team, we have enabled B2B communication using user defined service provider, where delivery method is email. We are using OAGIS channels. However, when PO is created, in collaboration messages, it shows that PO is sent or Delivery in Progress, but supplier doesn't get any email. How can I test end to end or make sure that it is getting delivered to Supplier.

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