Overview
Out-of-Office replies and calendar invites route through email servers owned by Microsoft (Office 365) or Google (Gmail/Workspace), rather than your corporate email server where Opensense is configured. This routing behavior impacts how Opensense can handle these message types.
Calendar Invites
Opensense does not stamp calendar invites by default due to inconsistent behavior and functionality issues.
Why calendar invites are not stamped
Calendar invites are system-type messages, not standard emails, and should not be treated as such. When Opensense processes these messages, several issues occur:
Loss of functionality – When Opensense touches a calendar invite, it converts the message into a standard email, causing it to lose its calendar invite functionality.
Inconsistent signature application – Stamping can produce unexpected results. For example, if a signature user sends an invite to a non-signature user who then forwards it, Opensense may apply a signature using a mixture of data from both users.
Poor calendar display – The plain text block of the signature can appear in the actual calendar tile, cluttering the calendar view and creating a poor user experience.
This limitation applies to both Microsoft 365 and Google Workspace environments.
Out-of-Office Replies
OOO stamping behavior differs between Microsoft 365 and Google Workspace. The sections below explain how each platform handles OOO replies and what is required for Opensense to stamp them.
Microsoft 365
How Opensense identifies senders
By default, Opensense reads the MAILFROM: header to determine which mailbox sent the email and apply the correct signature. When a user sends a standard email, this header contains their email address and Opensense can match it to their account.
When Out-of-Office and automatic replies are sent, Microsoft Exchange leaves the MAILFROM: header blank. Because this header is empty, Opensense cannot identify the sender or apply the correct signature. This is why OOO replies are excluded from stamping by default.
What is required for OOO stamping
To enable Opensense to stamp OOO replies, all of the following must be in place:
1. Email authentication (SPF, DKIM, and DMARC)
Your domain must have all three email authentication protocols properly configured in your DNS. Without these, OOO replies will send from a Microsoft address rather than the sender's own address, preventing Opensense from processing the message.
2. Mail flow rule adjustment
Your existing Opensense mail flow rules must be adjusted to stop excluding automatic replies. By default, these rules exclude OOO and automatic replies from processing. This adjustment must be completed by an Opensense Implementation Engineer.
3. Display From bypass
Because the MAILFROM: header is blank on OOO replies, Opensense must be configured to use the Display From address instead. This setting allows Opensense to identify the sender when the MAILFROM: header is unavailable.
Important: Enabling the Display From bypass changes how Opensense identifies senders across all email types, not just OOO replies. Organizations that use Send As or Send on Behalf in their normal workflows may experience unintended signature behavior. Before enabling, confirm with your Opensense Implementation Engineer how your mailboxes are configured and whether these features are commonly used in your organization.
Workaround: Manual signature in OOO message
If enabling OOO stamping is not viable for your organization, users can add a signature directly to their OOO message when creating it.
Use a text-based signature rather than an HTML signature with images.
Images cannot be uploaded to OOO messages. They either fail to save or break immediately after.
Copying and pasting a fully rendered HTML signature also fails. Images may break immediately upon saving.
Google Workspace
Google allows plain text signature blocks in OOO messages. Users can input the plain text version of their signature directly into the body of the OOO message, and it will route normally without additional configuration.
Opensense Support
For further assistance, contact Opensense Support:
Email: help@opensense.com
Knowledge Base: help.opensense.com