We have created a new "Plain - no background" stationery that can be used in place of the current one causing this issue. If you experience an email generating a red background, you can select the new Plain stationery for future emails which should resolve the issue by removing the body's transparent background color attribute.
From Content in the left side menu, select Stationery. In the drop-down menu at the top left, select Plain - no background. To use this new stationery for all new future emails, check the Default checkbox.
Additionally, you can select this stationery while creating an email or template. Within the email builder, in the Design tab, select “Stock: Plain - no background” from the Stationery drop-down:
It was reported that some emails were displaying a red background to Outlook mail users, even though the email used showed a white background in Act-On’s email builder and preview. We discovered that the emails were using Act-On’s built-in Plain stationery which has an older attribute in the code that the Outlook mail client may not properly support.
August 26, 2022.