We know our customers depend on their email and we work hard to try to make sure every email gets through to its destination. Despite our best efforts, due to the nature of email, messages can be rejected due to issues outside of our control.

This guide shows you how to resolve issues with email being rejected by TrustManager, an email software provided by Clearswift Secure Email Gateway.


Email is being rejected.


Your email is working normally, but when you email a specific email address your email is being rejected and returned to you with a non delivery receipt (NDR) similar to the below.

From: Mail Delivery System [mailto:Mailer-Daemon@server.example.com]
Sent: 20 June 2018 09:31
To: John Smith
Subject: Undeliverable: Example Subject

Delivery has failed to these recipients or groups:
A problem occurred during the delivery of this message to this e-mail address. Try sending this message again. If the problem continues, please contact your helpdesk.
The following organization rejected your message: mailhost.recipient-server.com.

Diagnostic information for administrators:
Generating server: server.example.com
mailhost.recipient-server.com #… Rejected – TRUSTmanager>


The recipient’s mail server is running an application called TrustManger, part of an email server application called Clearswift Secure Email Gateway. The system is misconfigured to block email from your domain. It might be someone has incorrectly flagged one of your emails as spam — so we’re delivering the email, but they’re rejecting your email.

All major email servers have what’s known as a sender reputation which acts a bit like an individuals credit-score. Email providers, including ourselves, use the reputation to determine the quality of emails being received from third-party mails servers. A server with a ‘good’ reputation (the highest score possible) is less likely to be a source of spam email.

All our mail servers have a ‘good’ reputation, meaning higher deliverability rates. This includes a good reputation with Cisco Systems Talos the main database. To maintain our reputation, we monitor our systems in realtime to enforce a strict zero-tolerance spam policy and to alert us to any changes.

They should not be blocking your email as it is being sent from an Ecenica email server with a ‘good’ reputation.

Unfortunately in this case the email system blocking your email address is not using a recognised sender database.


Unfortunately Clearswift do not provide an easy way of requesting blocks to be removed from their central database.

Contact your recipient and ask them to remove your email address from their local TrustManger blacklist.

If you do not have an alternative contact, try emailing postmaster@example.com, replacing example.com with their domain name.