A plain text email is created automatically for all marketing emails. This version is only sent to a recipient if the rich text version isn't supported in their email client. You can customize the plain text version of your email in the Plain text tab in the content editor.
Please note: after the plain text email is customized, it won't update with any new content changes made to the rich text version.
To customize the plain text version of your email:
In your HubSpot account, navigate to Marketing > Email.
Hover over the email you want to customize and click Edit.
Click the Settings tab.
Click Plain text and web version.
Under Plain text, click Customize.
In the dialog box, make any changes to your plain text email, then click Update.
Emails with smart content
If you're using smart content, the smart rules you've set will automatically apply to the plain text version of your email too. The default content will always appear in the Plain Text tab of the editor. If you customize the plain text version of an email that contains smart content, your smart rules will no longer apply in the plain text version.