Keeping track of who reported an issue.

Making sure we don't open Mantis to spam.

Making sure that users don't spoof the email FROM address to impersonate other users.

Support different types of email formats and protocols (e.g. POP3).

Making sure a company keeps control on the issues in their bug tracker (i.e. make sure no one can report a single issue that has viagra links). A company doesn't want their customers to login to their bugtracker and find porn and viagra related issues.

Support some sort of way to annotate email messages (e.g. setting attributes other than summary, description and project).

Disallow/allow unknown users from submitting issues

Unknown users should require a reply validation hash to prevent spamming of the issue tracker.

The reporting by email feature should be disabled by default.

Ability to retrieve email messages from POP3 accounts.

Support for one email account per project or one for all projects.

Use one dummy account to associate with all emails, in this case the originating email address should be included in the issue description.

When an event triggers a notification to the reporter of the issue, this should cause an email to be sent to the email address from which the issue was reported. This should be independent of whether we set the reporter as a dummy account or a real account.

Attachments to emails or replies to notifications should be added as attachments.

Handle mime/multi-part emails.

Support looking up a Mantis account based on an email. If an account if found use it, otherwise, there should be an option to reject the email or auto-create the account.

When a user reports an error via email, a confirmation email should be sent to the originating email address.

An idea to avoid spam is to send back an email that requests a certain interaction that the user needs to do. This would probably stop bots but not manual spamming.