Why should that be a concern? Many corporate mail servers use spam control services like those provided by mail-abuse.com. If a server on the blacklist is attempts to deliver a message to a mail server that subscribes to these spam control services, the message is is silently rejected. The sender of the message will only learn about the rejection a few days later when an "undelivered message" warning is sent back to him.
Compounding the problem is the fact that Google's mail support system is a shambles. If you go to the gmail help page and search hard enough, you will eventually find a link (four clicks away) that takes you to an on-line problem report form.
You really have to want to find that problem report form — it is very well hidden. It is almost as if the Google mail support team doesn't want to be bothered with reports of problems with their product. I'll save some of you the trouble of hunting it down — here's the link:
The persistent few who do find their way to this link will be rewarded with an auto response email message that says something to the effect that the Google mail support team is immensely happy that you took the time to report a problem, and that they are terribly sorry you were experiencing difficulties with gmail, but that they are horribly overworked and can't be bothered to give you any more attention now, thank you very much.
Now, I personally happen to think that the gmail application is pretty slick. However, if it won't deliver my mail reliably it's of little use to me, and I won't be recommending it to anybody else.
— Doug Roberts"