Hello @Troop9Weymouth ,
Our devs are looking into similar reports of this issue, and why it seems to affect some addresses, while not affecting others.
In the meantime, you can try using a URL shortener, such as bit.ly or tinyurl, and see if that can be inserted as a webpage link. If it still errors out, or it won't properly prompt the email in your tests after trying the URL shortener, then the only other workaround in the meantime would be to leave out the ?cc= element when constructing your mailto: link.
The tinyurl seems to work well in testing. Do you know if mailto or tinyurl in ConstantContact is likely to trigger spam filters?
I hope the developers can figure that out soon. I think I wasted a solid hour going back and checking my HTML syntax.
Unlikely, as mailto: is a basic coded function for email programs, and doesn't require leaving the email program to open since it's meant to prompt the program to start creating a new email. A shortened URL version of this shouldn't affect that functionality, or the receiving network's ability to detect it.
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