Received someone else's HMRC PAYE correspondence: cannot forward and cannot phone HMRC

HMRC has erroneously included communication for another individual along with mine. I live outside the UK so am not able to call early in the morning UK time when the phone lines are less busy. I've called 3 times not and been on hold for over over 2 hours in total. I do understand that this is a busy time for HMRC but this looks to be a time sensitive matter for the intended recipient. Can I post it back to HMRC and if so, what is the best address to use? Any other guidance? I do want to help but am a bit hamstrung.

Hi,

Please send it to the address in the link below. Please also include a covering letter advising that you have received mail which was not intended for you.

Income Tax: general enquiries#

Thank you.