It's not mildewed. I just washed it about a week ago. It gets the smell from fabric on it. I dislike any smells and pre-wash quilting fabric and donated all the fabric I can't get fabric softeners or perfumes out of.
I ironed some of my husbands clothes, and voila, the smell is back. I know now why estate sales and thrift stores have "that" smell, it's because the detergents and softeners and perfumes get rancid after a while.
I use odor free Tide but it is going to take a while to get all the smells out of the clothes. It just gets stuck in there after a while. I emptied my whole closet and used "sanitize" to get rid of that estate smell! I haven't emptied his whole closet yet though -- I'm waiting for him to choose which clothes he wants to keep. I'm going to use a towel over the ironing board for his stuff from now on.
It is just hard to take all the staples out to wash my ironing board so I'm hoping for some spray on odor remover other than vinegar to use on a daily basis.