Does sending dinars electronically to buy euros, which are then electronically transferred by the seller, count as constructive possession?

This transaction is permissible and is considered a constructive possession (qabd hukmi) which takes the place of actual physical possession (qabd hissi), provided that the transfer occurs simultaneously. The banking entry of a sum of money into the customer's account is considered a valid constructive possession, both religiously and customarily, whether through direct deposit, bank transfer, an immediate exchange contract between the customer and the bank, or by the bank deducting an amount from one account to another at the customer's instruction. A delay in the banking entry is forgiven to the extent that it enables the beneficiary to actually receive the funds within the customary periods, provided that the beneficiary does not dispose of the currency during this period until the effect of the banking entry occurs, making actual receipt possible. The session of the contract ('majlis al-'aqd') is the period of communication between the contracting parties, as long as the discussion pertains to the contract.