Why does a mailto link that works in browserX doesn't work in browserY?
The mailto link (
mailto:firstname.lastname@example.org,email@example.com?subject=Join) assumes that the protocol between browser and email client is based on RFC2396, but mostly this is a false assumption, and most of the programs use RFC822 (where ? is an illegal email address character).
The curious thing is that Internet Explorer using Outlook Express works fine, so does Opera and its Opera mail client. But the mailto doesn't work when Interner Explorer uses OperaMail as the client, and when Opera uses Outlook Express as the client.
The solution is patently obvious - use a server side solution.