Use BoxTrapper in cPanel to stop spam with sender verification

BoxTrapper is a challenge-response spam filter. When someone who is not on your whitelist writes to you, their message is held and they receive an email asking them to confirm they are a real person. Once they reply, the message is delivered and they are whitelisted. It is very effective against bots but has side effects, so read the last section before enabling it on an important address.

Before you start

• Access to cPanel and the mailbox you want to protect.
• Try Spam Filters (SpamAssassin) first; it works silently and suits most mailboxes.

Enable BoxTrapper

1. Open cPanel → Email → BoxTrapper. If it is missing, the feature is disabled on your plan.
2. Find the mailbox in the list and click Manage.
3. Click Enable. The status changes to Enabled.

Configure the settings

1. Click Configure Settings.
2. In Email addresses going to this account, list every address that delivers to this mailbox (aliases and forwarders), separated by commas.
3. Set Your Name; it appears in the verification email.
4. Set Number of days to keep logs and messages in queue (for example 15). Unverified mail is deleted after this.
5. Set a Minimum Apache Spam Assassin Spam Score required to bypass BoxTrapper if you also use SpamAssassin.
6. Click Save.

Build your lists

• Edit White/Black/Ignore Lists: add rules for senders who must always get through (customers, payment providers, your own domains, @paypal.com), senders to reject, and senders to drop silently.
• Add newsletters and automatic notifications to the whitelist before enabling; they cannot answer a challenge.
• Use Edit Confirmation Messages to rewrite the challenge email in friendly language.

Review the queue

Open Review Queue regularly. Select a held message and choose Whitelist to deliver it and trust the sender, Deliver to release it once, or Delete.

Disable BoxTrapper

Go to cPanel → Email → BoxTrapper → Manage and click Disable. Release anything important from the queue first.

Next steps

• Set up SpamAssassin spam filters
• Create email filters
• Stop your own mail going to spam