Laundry has a foul odor after washing. Washer is practically brand new. Can anyone tell me what would cause this? Someone suggested it may be a clogged ventilation pipe that exits on the roof, but I do not know how to check for this or what to do if it is clogged? Any suggestions?

Thanks.

Not your vent stack unless by foul you mean like sewage. Its likely lint and grease catch in the machines filetrs that's starting to rot. Have you ever smelled anything like this smell before, what was it?