Email security settings

The Email Security Settings allow administrators to configure security and control rules applied when sending emails from the platform. These settings help prevent abuse, restrict recipients, and sanitize email content before delivery.

You can access these settings from the Tenant Environment Configuration panel, under the Email Notification section, by clicking the Configure Email Security button.

Settings

The Email Security Settings modal provides the following configuration options:

• Maximum recipients

Defines the maximum number of recipients allowed per email sent through the platform (To + Cc + Bcc). If set, any email exceeding this limit will be rejected. Leave empty for no limit.

This is useful to prevent mass emailing or accidental broadcast to large audiences.

Example: Setting this value to 50 means no email can be sent to more than 50 recipients at once.

• Sanatize tokens HTML 

When enabled, all HTML tags are automatically stripped from token values before they are injected into email templates. Only the plain text content of each token is kept.

Use case: This is particularly useful when token values may contain user-generated HTML content (e.g., rich text fields from SharePoint). Enabling this option ensures that no unexpected or potentially malicious HTML markup is included in the outgoing email, improving both security and rendering consistency across email clients.

Example: A token value of <p>Hello <strong>World</strong></p> will be sanitized to Hello World before being inserted into the email body.

• Allowed Email Domains

Restricts the recipient email addresses to a specific set of domains. When configured, only email addresses belonging to the listed domains will be accepted as recipients. Any recipient with an email address outside of these domains will be filtered out.

Example: Adding contoso.com and fabrikam.com ensures emails can only be sent to addresses like user@contoso.com or user@fabrikam.com.

• Allowed Image Domains

Restricts the image sources (<img> tags) allowed in the email body. When configured, only images hosted on the listed domains will be kept in the email content. Images from other domains will be removed during sanitization.

⚠️Note: System images (cid:) are always allowed regardless of this setting.

Example: Adding cdn.contoso.com ensures only images hosted on that CDN are included in outgoing emails.

• Allowed Link Domains

Restricts the hyperlinks (<a> tags) allowed in the email body. When configured, only links pointing to the listed domains will be preserved. Links to other domains will be removed during sanitization.

Example: Adding contoso.com and sharepoint.com ensures only links to those domains are kept in the email content.

How to configure

1. Navigate to the Tenant Configuration page.
2. Under the Email Notification section, click the Configure Email Security button.
3. In the modal that opens:
   • Set the Maximum Recipients value if you want to limit the number of recipients per email.
   • Toggle Sanitize Tokens HTML to On if you want HTML tags stripped from token values.
   • Use the Add Email Domain / Add Image Domain / Add Link Domain buttons to define allowed domains.
   • Use the Delete button (🗑) next to a domain entry to remove it from the list.
4. Click Save (✔) to apply your changes, or Cancel (✖) to discard them.

Notes 

• When a domain list is left empty, no restriction is applied for that category.
• Domain entries should be specified without the protocol (e.g., contoso.com, not https://contoso.com).
• Wildcards are supported for Email and Link domains (e.g., *.contoso.com).
• Changes take effect immediately for all subsequent emails sent from the platform.