We're very sorry for any errors that occurred when your friend tried to sign up for your mailing list, and we definitely want to help! Thanks so much for letting us know so we can track this system issue for our engineers who are working to fix it as quickly as possible.
In the meantime, you can add the URL to your sign-up form in the body of any email campaign, or you can add it in the Forward to a Friend email message. To do the latter, just click your name in the top right and select My Settings, then click Email Features and Edit Your Forward Email to a Friend Email:
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