Blocked Recipients: Why Email Stops Reaching Someone
Check whether an address is blocked, see why, and switch sending back on once their mailbox is working again.
Sometimes an email you send never arrives, and every send after it fails too. Usually that means the address has been blocked. TrustPager keeps a list of addresses it can't currently reach, and the Blocked recipients tool lets you check any address and switch sending back on once the problem is fixed.
Where to find it
Go to https://app.trustpager.com/settings/email and find the Blocked recipients card. Type the address you want to check and press Search. You only see addresses your own workspace has emailed or holds as a contact.
Why an address gets blocked
- Bounced. The mail server rejected the message because the mailbox does not exist. This is the most common cause. It happens when someone leaves a company, a mailbox is deleted, or a domain lapses or expires. It can also happen to a mailbox that works: if that mailbox forwards its mail to an address that no longer exists, the forward bounces and the original address is blocked.
- Reported as spam. The recipient marked one of your emails as spam.
- Manually blocked. Someone switched sending off for that address deliberately.
Blocking is automatic and it is there to protect you. Mail providers judge a sender by how often their mail bounces, so continuing to send to a dead mailbox would damage delivery for every other email your business sends.
How you can tell an address is blocked
Every email that isn't sent because of a block shows as Blocked at https://app.trustpager.com/data/emails, with a line saying why and since when, for example: "Not sent: this address bounced on 22 July 2026 and is blocked. If the address works, unblock it at https://app.trustpager.com/settings/email". Automations that tried to send show the same line on their run, so a step that sent nothing tells you why.
Get told when an address is blocked
The Email Bounced automation trigger fires when an email you sent bounces. When the bounce has blocked the address, the trigger includes address_blocked (true) and blocked_at (when it happened). Build an automation on it at https://app.trustpager.com/auto/automations to alert whoever relies on that address, for example a task or a message to your team, so a person doesn't quietly stop receiving reports or notifications.
The mailbox works but it keeps getting blocked
If the person is receiving other email fine, check whether their mailbox forwards to another address, or is a group with a member who has left. When that other address no longer exists, every email to them bounces a few seconds after it arrives and the address is blocked again. Remove or fix the forward first, then reactivate.
How to switch an address back on
Only do this once the underlying problem is actually fixed, for example the person has their mailbox working again, or the expired domain has been renewed. Reactivating an address that is still dead just recreates the same failures.
- Go to https://app.trustpager.com/settings/email.
- Search for the address in the Blocked recipients card.
- Check the reason shown beside it.
- Click Reactivate and confirm.
Sending resumes straight away. Reactivating clears the block everywhere it applies, so automations, forms, signing requests, campaigns and one-off sends all start reaching the address again, and the contact goes back into your marketing audiences if the block was the only thing keeping them out.
Reactivating never overrides a genuine unsubscribe. If the person had also unsubscribed from marketing email, that choice is kept: they get your normal emails again (bookings, invoices, signing requests) but not your marketing. See https://trustpager.com/help-center/email-opt-out-handling.
Turning a contact's email back on is not the same as unblocking
Switching a contact's Email opt-out back off on their contact page (or the person clicking "resubscribe" in one of your emails) lifts their own choice: a marketing unsubscribe, or a do-not-contact request. It does not lift a bounce or a spam complaint, because the mailbox is still the problem. If a block is still in place, the contact page tells you and offers a button straight to https://app.trustpager.com/settings/email, where you can reactivate the address once it works.
When an address cannot be reactivated
If the recipient reported one of your emails as spam, the block cannot be lifted from here. That is a deliberate protection: sending again to someone who reported you as spam puts your whole sending reputation at risk. The card tells you when this is the case. If they want your email again, ask them to contact you first and get in touch with support.
Confirm it worked
Send one real email to the address, then open https://app.trustpager.com/data/emails and check that the send shows as Delivered rather than Failed. Do that before you point anything important back at the address, such as form notifications or a signing recipient.
From the API or an AI agent
The same list and switch are available to the TrustPager API and to AI agents connected over MCP: list_blocked_recipients shows the blocked addresses (pass part of an address to search), and unblock_recipient switches one back on. Unblocking needs the email settings write permission. Full details: https://docs.trustpager.com.
Who can do this
Workspace admins. If you can open https://app.trustpager.com/settings/email, you can check and reactivate addresses for that workspace.