Due to the scammers and spammers of the world, instead of sending a complete stranger your email address when you make contact with them and listing a phone number that members can see if they are on your site , can a plugin be made to send someone a code number instead of your email address. This is used on Craiglist.org , and it helps keep spammers and scammers from stealing your email address and phone number since they have to be verified by Captcha  or as a member if this is set by the owner of the ad. I will include a screen shot of an ad that shows this in process. Can we get a plugin made that can send a code number to the recipient as this will hide the senders email address. Also the recipient can reply back in the email that was sent with the email code. If you need to see this in action then you will need to test it yourself on that site.   

@Sparky
It does not make too much sense.
I suppose if you reply to that mail (with code), email will be re-routed to person behind this mail, it is not just random code.
Next, this has no effect against spammers.
Last, you can allow usage of contact form to logged-in users and these will have to deal with recaptcha.

From my point of view, it is just ton of work with no real effect.

 What it does is take the email address out of the public eye from everyone, so there are no one trying to steal your email address or hacking into your personal accounts plus all the other benefits that it includes, spammers, scammers and such things. So I think it has a good sense to it. If members or non members can not see your email address, then it is a great safety feature which i really want to have in my site. I personally don't want my personal email address listed on any site that is very vulnerable to scammers or hackers. I block many everyday in my site already and have not even really started using it. Recaptcha is just another word for band-aid and really has not much effect or a lot of safety to it, unless your a bot and even then it is not 100% safe.  I just want a safe site for members and their personal information more secure that what is available with most scripts. So maybe some developers can come up with some other alternatives for us to add some more safety features and not show email address or phone numbers when sent to a seller as a buyer, and in return from them. The members that post their emails and phones and want them seen, that is there choice, but I would like to see other safety features myself. This is one question i get asked , can people see my email address if i send them an email. They don't like it cause they don't know them, the are Strangers.

@Sparky
Spammer will not get your email as notification is sent to you, not to that spammer and you can decide whether it is spam or not and reply or not.
As example, what is purpose of having Phone number input in contact form, if seller do not get this phone number once notification is sent to this user? Does not make sense.

Messaging inside Osclass , like direct messages in forum can do the trick, and there’s such plug-in.