Ever had the situation where, even though you have given permissions to edit nodes to a role, and assigned that role to a user, they still can't edit the node?
Drupal will stop people from editing nodes that use a filter format that they don't have permission to use. So check that the filter in use by the node is available to the user in question.
A simple "Contact" form on a website. The form allows people to enter their name and e-mail address, so that the message appears to come from them, and the site owner can use their Reply button to reply to the sender (and not the web server!).
The problem is defining what the "sender" e-mail address is, which is then compared with the address's domain's SPF record to see if it is coming from an authorised mail server.
