Bullying and harassment is a totally different procedure. You have two choices, you may either warn the person yourself or ask your manager to do it, this is stage one and basically amounts to a ticking of (depending upon the level of bullying or harassment) of which can go higher.
Past this, is the more serious level where your complaint does become serious, with witnesses and statements. It becomes a conduct code issue and can have serious repercussions. All must be based upon fact, witnesses etc.
You can simply state you was depressed or anxiety because of these issues and couldnt work but wont cover your absence in any form an will mount up on your stage warnings.
If in doubt, confront all harassment and bullying to your manager, or your manager manager, it is all unacceptable behaviour.
Also understand that for most issues, a postperson deserves there first verbal warning, sometimes peoples behavior may seem unacceptable to you but horseplay is part of the business that we work in, he/she deserves the ticking off just to let him/her know they,ve crossed a boundary.