Thank you very much for your question. I have found that sensitivity in the hind legs and kicking out is a very common problem with mares. To understand why your mare is behaving in this way, you need to understand how nature has `wired` her!
A mare in the wild essentially fulfills two roles - she is either there to have foals and enlarge the herd or she is also an alpha mare and is also partly responsible for the rest of the herd. The herd stallion will `tease` each mare to see whether she is ready to be covered or not, and he does this by gently nibbling at her hind end... A mare that is pregnant or is not receptive to the stallion will let him know immediately by squealing and kicking out. A mare that is in heat will also squeal and may even kick out, but will become less so as she is ready to be covered. A mare with a foal at foot needs to protect her foal from the herd stallion and other mares, and she uses physical language to do that - biting, kicking and charging. So what I am trying to tell you is that a mare communicates with her hind legs! Stallions, and to a lesser degree, geldings, tend to communicate with their mouths (biting) and forelegs (striking out) but mares are more likely to kick out behind. Also, your mare is wired to strike out behind if she is uncomfortable with any physical contact with her hind end. Understanding this will help you see that she is just sticking to the way nature has programmed her and that you should not be getting impatient or losing your temper with her, instead you should be teaching her to feel more comfortable with you handling her hind legs. If your mare is kicking out a lot in her stable, she is most likely doing so in response to the attention she is getting from her neighbour! If you can move her to spot where she only has one horse next to her, and then you pick that horse carefully, (try a few and see who she is happy to be next to) you may find that the kicking will get less.
If she is kicking the door with her front legs, especially at food times, you will need to do one of two things - remove the door or prevent her getting to it, or you must protect her legs. Removing the door and replacing it with a chain, pole or some other type of non-solid structure will mean that she has nothing to bang against. You may have to consider some type of boot protection for her legs plus padding the door with rubber if you are unable to remove it.
When handling her hind legs, I would like to make the following suggestions:
You will need to slowly desensitize her to being handled behind. I would suggest that you spend as much time with her rubbing her all over with a soft cloth, picking up her front legs, rewarding her for allowing you to do so. Please wear a riding hat or some form of head protection - never ever take a chance with a horse that might kick. I have been kicked in the head by a mare`s hind legs while working on her front legs and let me tell you it was so quick I did not see it coming! If I was 2 cm to the left she would have killed me for sure. Have someone hold her head or give her a teff net to munch on if it relaxes her. Start in front and wherever you know she does not mind being handled. Gradually move your way to where she does not like being touched, all the while keeping calm, gentle and talking to her. The aim is to touch and retreat before she actually gives you a negative response, reward her for that and repeat. If she actually kicks out or moves away, then you have gone too far. You will notice that each time you will be able to rub her more and more. Once she is happy with you rubbing her all over and is comfortable with that, you can gently ask her to lift a hind leg, then put it down gently and reward her. Do not lift her leg too high, don`t drop her foot if she lifts it very quickly and don`t put her in an uncomfortable position. Watch her body language and that will guide you. If she does get very difficult, go back to the front legs and start all over again. Keep the sessions short, do not carry on if she gets very difficult - rather take her for a walk in hand, bring her back and start again.
I must stress that working with a horse in this manner can be VERY DANGEROUS and that you should NEVER risk your own safety! Use protective gear if you must, refer her to a qualified person who can help you, and never be scared to ask for help. If you are not 100% sure of what you are doing, rather do not take the risk. Even a soft blow from behind can be enough to kill you, so please do be safe first! Even though you do say she does not usually kick, I can promise you that under the right circumstances the biggest plod can become a maniac! Whenever I work with any mare I always remember that it is in their nature to communicate with their hind legs! Never take your focus off her for a second.
When working with any horse, always remember to use repetition, patience, consistency and confidence - horses respect that!