We're ending support for raw HTML and CSS in custom email templates on Friday the 16th of August this year, just over 4 weeks from now.
We advise that if you are using custom HTML email templates that you transition these to our new improved plain text / markdown custom email templates before this date. Any templates which have not been manually migrated will be automatically changed to use the new plain text / markdown custom template format during the week commencing the 12th of August.
If you have used custom HTML email templates to apply branding to emails you will be glad to know that with branding enabled on your account these new plain text / markdown custom email templates automatically include branding as specified for your account.
For more information on how to migrate your custom HTML email templates to plain text / markdown templates and how to re-create basic markup with Markdown please refer to our support article or contact the customer support team and they can make these changes on your behalf.
We realise this may feel like a frustrating and unecessary adjustment but the new plain text / markdown custom email templates provide a more consistent look and feel, offer greatly improved readability and reduce false positives from phishing and/or spam filters.
Ultimatley these changes ensure that users are more likely to recieve and read emails you send and act upon them in a timely manner - which is a better result for you and your users. If you have any concerns about this change don't hesitate to speak with your account manager.