What lph siad. It really matters what tone it's said in. A real true friend might express their sorrow to another friend and use "but" to add a comforting thought to the sentence. However, I don't believe "but" is necessary because to me it has bad connotations and tries (like others have said) to mitigate the words that come next. Sometimes that is appropriate. Yet tt is far more powerful to simply say to someone I'm sorry. If that is what you mean and then follow it with a new statement without "but". Sorry is powerful enough on it's own.

It reminds me of something I have heard younger kids, say 15 years old and younger that goes like this...."not to be rude or anything, but"...I've heard them telling this to their friends and I find it strange. So does proclaiming that you are not rude mitigate the fact that you are about to do something that is? That logic just cracks me up.

But is only three letters long but it has a pretty big meaning.