My bathroom sink is draining very poorly. I snaked out the pipe, but found no clog.
A plumber came for the same problem about a year ago and blamed it partly on our sinks overflow being very rusty and interfering with proper venting of the sink.
Does this sound right and can the overflow be effectively reamed out? I can fit a wire snake through it now, but not sure if anything much bigger would make it.
Thanks!

I disagree with your plumber. Is the stopper rising high enough? Have you tried using a plunger?

Thanks Doug.
I had tried the plunger and removed the stopper, with no luck.
We had another plumber in yesterday and he went further in the line and found a clog.
He also thought the rusty overflow theory was bunk.
Thanks again.

I agree with Doug, Your plumber's blowing smoke. Unless you have a "S" trap on the lavatory you have a vent running through the roof. Regards, Tom