Custom party URLs are a great way to give your party some personal flair and improved marketability. However, just like with regular domain names on the Internet, conflicts with regards to naming may sometimes arise. This is known as "Cybersquatting". You might find that a URL that would have been perfect for your party is already taken, which can be frustrating. The easiest solution is to think of a different name; easier said than done!
The trouble with Cybersquatting is that disputes are generally settled based on trademark law. Sonlet cannot mediate such disputes.
When URL disputes do arise and a different name cannot be settled on, the first thing you should do is try reaching out to the owner of the party. You can do this by sending an email to the address shown in the error message text when you try to use that URL.
In order to transfer a party URL to another user, the easiest way to do it is to just agree on a time that you'll relinquish the URL (by unchecking the "Custom URL" checkbox on the party details form). After that time the other party can claim that URL using the party details edit form like normal. That does mean that there could be a short window of time wherein an unknown third party could swoop in and capture that URL. To avoid that, the party owner can send an email to firstname.lastname@example.org and we'll execute a direct transfer of the URL for you.
If you don't want your email address exposed when other people try to claim your URL you can set up another Sonlet account using a different email address to be the "holding" account for your domains. That other account would then add your original Sonlet account as an admin in your parties.