Because I am an active NameJet bidder, I have quite a few domain names at Network Solutions. Because of the pricing deals I am offered elsewhere, I tend to transfer out my domain names before they expire.
VisitWillemstad.com is a domain name I won on NameJet. After receiving several expiration notices for this domain name, I transferred it to my Enom account. On August 3, Enom emailed me to confirm that the transfer was successful. A Whois search confirms that this domain name is registered at Enom.
This morning, I received an email from Network Solutions imploring me to renew this domain name:

How the heck can I renew a domain name at Network Solutions when it already transferred to Enom? Obviously, I can’t do that.
Fortunately for me, I have a relatively small domain portfolio and I stay on top of renewals and transfers. Someone else might get confused and try to renew this domain name that was already transferred. I assume Network Solutions would not charge for a renewal on a domain name that is no longer registered there, although it might be frustrating to call and waste time with that. I did not call to see if they would process a renewal, so I can’t say whether or not this would happen.
In my opinion, Network Solutions should check to see if a domain name is still registered there before sending this type of email. It can be a bit confusing, especially for a person or company with a large domain name portfolio.