With regards to..

[Yueehs]

Do these sound natural?

1) Please refer to the email below with regards to your room reservation.
2) Please refer to the email below regarding your room reservation.

 

[Rover_KE]

I'd only use #2.

 

[Yankee]

Do these sound natural?

1) Please refer to the email below with [STRIKE]regards[/STRIKE] regard to your room reservation.
2) Please refer to the email below regarding your room reservation.

1) with correction or 2) as posted.