Name the applications and describe what someone does by hand between them. Add one normal record and one case that caused trouble: an amendment, missing account reference or interrupted transfer.
Information to gather
Explain the timing, source and destination references, and who can confirm the business rule. Identify the person who can arrange technical access. You do not need an architecture or development estimate before the discussion.
Remove personal details and confidential prices from sample records. Do not send credentials or a database export in an initial message.