--- title: "Email Relay for Office 365: Introduction, Requirements, Troubleshooting, and FAQs" slug: "introduction-15" updated: 2026-02-03T19:51:57Z published: 2026-02-03T19:51:57Z canonical: "docs.trustifi.com/introduction-15" --- > ## Documentation Index > Fetch the complete documentation index at: https://docs.trustifi.com/llms.txt > Use this file to discover all available pages before exploring further. # Email Relay for Office 365: Introduction, Requirements, Troubleshooting, and FAQs #### Introduction This instruction manual is designed to guide you through the configuration, use, and troubleshooting of Trustifi Email Relay within Microsoft Exchange Online via Office 365. The document includes all necessary requirements, step-by-step configuration procedures, usage guidelines, and troubleshooting recommendations to ensure a successful deployment. Please follow each step carefully and pay close attention to all warning notes throughout the process. --- #### Requirements To configure your email environment to work with Trustifi Email Relay, you must have: - An Office 365 administrative account with permissions to access and manage the Microsoft Exchange admin center - A Trustifi account with administrator permissions - Administrator access to your DNS management system --- ### Troubleshooting #### TLS Authentication Failed **Detailed Log** Couldn’t validate the recipient’s email server certificate. The certificate isn’t signed by a trusted certificate authority. **Solution** The incorrect certificate was selected. Please return to the relevant security settings step in the configuration guide and select the appropriate certificate. --- #### Email Error **Detailed Log** The email you specified is an Office 365 mailbox. To validate this connector, please specify an email address that is not hosted in Office 365. **Solution** Use an email address that is not hosted in Office 365, such as Gmail, Yahoo, or Hotmail, and retry the validation step. --- #### Domain Does Not Exist **Detailed Log** 550 [X.X.XYZ](http://X.X.XYZ) DNS domain [bad-domain.com](http://bad-domain.com) does not exist **Solution** This indicates an incorrect smart host address. Please return to the smart host configuration step in the guide and update the value accordingly. --- #### Failure to Send a Message **Description** Messages are failing to send through the connector. **Solution** Review all configuration steps prior to connector validation to ensure each item was completed correctly. --- #### Emails Sent Without Styles or Formatting **Description** Emails are delivered using RTF formatting instead of HTML, resulting in missing styles or formatting. **Solution** Disable Rich Text Format as instructed in the Remote Domains configuration step of the guide. --- #### Automatic Replies or Forwarding Not Working **Description** Automatic replies, automatic forwarding, or Out of Office messages are not being processed. **Solution** Refer to the Remote Domains configuration step to enable external and legacy Out of Office replies. --- #### Meeting Invitations Missing Reply Options **Description** Meeting invitations are delivered but do not contain Accept or Decline options. **Solution** Enable Out of Office and related functionality as instructed in the Remote Domains settings. --- #### Email Sent Without the Trustifi Connector **Description** The message was sent and delivered but did not pass through the Trustifi secure connector. **Symptoms may include** - Missing email wrapper - No Trustifi logo, footer, or header - Attachments delivered directly instead of as secure links - Links without tracking **Solution** This typically indicates a misconfigured mail flow rule or interference from other higher-priority rules. Review and validate all rules and ensure the Trustifi Outbound rule is prioritized correctly. --- #### Email Failed to Be Delivered **Description** The message was sent through the Trustifi connector but could not be delivered. **Solution** Validate the relay key in the message header as described in the mail flow rule step of the configuration guide. If the configuration appears correct, contact [Trustifi Support.](mailto:support@trustificorp.com) --- #### New Users Receiving “Welcome” Emails from Trustifi **Description** After the Email Relay connector is established, new users may receive a “Welcome” email upon sending their first message. This feature is optional. **Solution** 1. Log in to the [Trustifi Web Portal](https://app.trustifi.com/home) as an admin 2. Navigate to Outbound Management → Plan Settings 3. Select the [Email Flow Integration tab](https://app.trustifi.com/outbound/adminSharedPlan/emailFlowIntegration) 4. Scroll to **Send welcome email to new users** 5. Disable the toggle ![](https://cdn.document360.io/7285c856-097a-4601-acb7-48c358223827/Images/Documentation/welcomw toggle(1).png) --- #### Issues with Delivering Emails to Groups **Description** Emails sent to distribution groups or aliases may fail delivery or may be delivered multiple times. **Solution** 1. Log in to the [Trustifi Web Portal](https://app.trustifi.com/home) as an admin 2. Navigate to Outbound Management → Plan Settings → [Integrations tab](https://app.trustifi.com/outbound/adminSharedPlan/integrations) 3. Select the Microsoft Exchange integration 4. In the pop-up window, locate the Groups/Aliases section 5. Click **Sync** to refresh the group and alias mappings --- #### Issues with Encrypting Attachments **Description** Attachments are being encrypted automatically even though no DLP rules were triggered. **Solution** 1. Log in to the [Trustifi Web Portal](https://app.trustifi.com/home) as an admin 2. Navigate to Outbound Management → Rules and Policies → [Policies tab](https://app.trustifi.com/outbound/adminPolicyManagement/policies) 3. Scroll to the Attachments Encryption Policy section 4. Adjust the setting according to your organization’s requirements ![](https://cdn.document360.io/7285c856-097a-4601-acb7-48c358223827/Images/Documentation/encrypted attachments policy(1).png) --- #### Third-Party Signature Service Isn’t Working **Description** When using a third-party signature solution such as Exclaimer Cloud, signatures may not be applied after integrating Trustifi. **Solution** To ensure signatures are applied correctly: - The signature service mail flow rule must appear **before** any Trustifi mail flow rules in Exchange. - The signature service rule must have **Stop processing rules** enabled. - If you are using Trustifi for both outbound and inbound protection along with a third-party signature service, all three mail flow rules must have **Stop processing rules** enabled. **Correct Mail Flow Rule Order** 1. Signature Service Rule (e.g., Exclaimer Cloud) 2. Trustifi Outbound Rule 3. Trustifi Inbound Rule If the issue persists, contact [Trustifi Support](mailto:support@trustificorp.com) at [support@trustificorp.com](mailto:support@trustificorp.com). --- ### Frequently Asked Questions #### Will the Email Relay apply to everyone in my domain? Only if you want it to. During configuration, you can choose whether Email Relay applies to all users, specific groups, or selected individuals. --- #### Does the Email Relay affect my incoming emails? No. Email Relay only applies to outgoing email traffic. For inbound protection, refer to the [Inbound Relay integration guide](https://docs.trustifi.com/docs/inbound-relay-integration-office365). --- #### Will the Email Relay automatically encrypt all my emails? No. Emails sent via Email Relay travel over a secure channel, but content is only encrypted based on your configured DLP rules and policies. See the [DLP rules policies guide](https://docs.trustifi.com/docs/dlp-rules-policies-guide) for more information. --- #### Will the Email Relay automatically encrypt all my attachments? This depends on your attachment encryption policy in Outbound Management → Rules and Policies → [Policies tab.](https://app.trustifi.com/outbound/adminPolicyManagement/policies) --- #### I received a “Welcome” email from Trustifi. What does this mean? It means a Trustifi account was created for you. You may create a password to access the Trustifi web app or Outlook add-in, but this is not required to send email via the relay. --- #### Can I continue using the Trustifi Outlook add-in after enabling Email Relay? Yes. The Trustifi add-in works seamlessly with Email Relay and can still be used for sending encrypted emails and viewing tracking information. --- #### Is there a size limit for emails sent via Email Relay? - Email body limit: 6MB (including text, HTML, and inline images) - Attachment limit: 1GB