Some banks just need it for records. For example, in HDFC they send 1-2 emails a month for random purpose like OTPs and Transactional messages. No idea if IDFC wants you to send them an email from your office ID like how ICICI asks for some applicants.
For me, ICICI rejected my application in July because they couldn't get a response from my office ID despite telling them ICICI bank (at that time) was not whitelisted by our IT.