Hi so this is a bit confusing. I have been engaged to my partner for nearly two years and been together nearly three years. Everything was great at first and I got on with everyone until his mother started getting jealous, making snide comments and sending me abusive messages. Obviously me being me, I didn't take it laying down and made it clear that this behavior is not acceptable. However, now I feel as though things are being said and done behind my back and he doesn't tell me. When I say his family is crazy I mean they are jealous, manipulative and just plain rude most of the time which is why I don't really bother to get involved. They talk about each other behind their backs and then carry on as if nothing happened and everything is just great :D... :/

And most of the time is was said to me. So I'm thinking if they are b***ing about each other to me aren't they not talking about me to other people when they decide that I'm certainly not good enough? His mother is just clingy, inappropriate in every way and just plain annoying. I have confronted my partner on different occasions and usually he gets defensive and then retreats to saying he will have a chat to his mum, but then its brushed under the carpet and he keeps things from me such as letters, texts etc. Every time he talks to his family on the phone he gets uncomfortable and always turns down the volume because they don't know I'm there and probably does say snide things. Its just frustrating because most of my issues come with me not trusting his family. Is this guy really worth it and will it ever end?

If this is going on now, trust me, it will be worse after you are married. It will be constant drama upsetting your life. You need not bother planning a family Jo-Anne, because why would you want your children exposed to that dysfunctionality?

That's the thing when I have already put up a wall and have absolutely nothing to do with the family anymore. I don't ask about them and he does not really tell me anything about them and I certainly made am strong enough to make decisions about my children in the future to only be around them supervised. (alcohol and smokers don't mix with me). The problem seems to lie with him pretending that there isn't a problem there and even if I'm not involved anymore, somehow he is and I've learned that things go on and he doesn't tell me. I literally hacked into his email account (wrong I know, but I couldn't help it) to find things that his mother sends and found a bunch of letters from her making snide comments about me.
It is dysfunctional on their part and it makes me feel good to know that my family is amazingly cool compared to them, Is there a way to show this man that his family (mother) is poison?

They are what they are and probably will never change so be aware of how you handle these nuts, of which your husband is one. And so shall your kids be. He will be caught in the middle of all the conflicts you have with them, and is probably helpless as you are to change them.

Stop snooping and looking for dirt.

Is there a way to show this man that his family (mother) is poison?

NO. Give up and get out sooner rather than later.
PS: I am always wary of engagements that last more than a year. What's the delay?

Rule of thumb: When you marry, you marry your partner's family.

The situation will only get worse once children are involved.

That's the thing when I have already put up a wall and have absolutely nothing to do with the family anymore.
It won't be fair to your children (and they won't understand and will eventually dislike you for it) to keep your children away from a set of grandparents and that side of the family no matter how awful they are. Like J_9 said, you marry his entire family, like them or not, and your children are their blood relations.

''I have confronted my partner on different occasions and usually he gets defensive and then retreats to saying he will have a chat to his mum, but then its brushed under the carpet and he keeps things from me''
He should be standing up for you and telling his family that they need to mind their own business when it comes to you. To him its all normal because its what he grew up with. He isn't going to change mom, you can't change her, but he should stand up to her in your defense.

It sounds like they not only talk about you behind your back, but they talk about each other behind their backs as well. I assume your boyfriend is also a victim/participant in his family drama.

Those types of families in my opinion, are usually very tight knit. They need each other, and feed off each other, and their lives revolve around a common denominator of anger, distrust, disrespect, and low values. Their lives and their place in the world is only as important as those living it with them- the family.

You cannot change them, or their predictable patterns of behavior, but you can understand what your options and priorities are.

You love a man who has been part of 'the family' all of his life. But, he may very well be able and willing to set boundaries with you, which in turn will keep the two of you on an even, honest keel, when it comes time to deal with them.

I suggest that you stop putting the pressure on him, because he is between a rock and a hard place. He is probably trying to keep the peace, for your sake, and the sake of the relationship. I think he tries even harder because he knows very well that eventually, without some sort of plan, this will get worse and the relationship will end.

Get into couples counseling!! Together, the two of you can identify what you have control over, and what you have no control over. You can learn how, together, to set limits, and stick to them, with 'the family'. It matters not how 'the family' sees consequences that come their way due to their behavior, it only matters that the two of you set your own expectations, limits, and consequences. And stick to them.

The minute one of you cracks and that wedge starts to slice through the relationship, you have lost the partnership, together, that you need, to stay strong together.

I don't think 'the family' will change. They are too strong and too entwined to want to lose their lifelines- each other- and don't wish to change, or they would have.

Try counseling, and put the anger and resentment to rest, get beyond it with a plan, and you will be much stronger together in the future, than you are right now.

I hope you don't give up.

Give up the notion you need protection from his family by him. He probably does, but you won't see it. And as crazy as they are, look at the partner they have produced for you.