SendX allows you to create your own email templates from scratch and copy them using the drag and drop editor with ease. But, the drag and drop editor doesn't allow you to upload a full HTML email template. In order to upload your designer's work on to SendX, you're required to change the email editor to a Plain Text Editor.
SendX allows you to quickly change your email editor of Campaigns from Drag and Drop to a Plain Text Editor. You can do so by following these steps.
Go to Settings > Preferences, where you will get the option to change the Default Email Editor from Drag & Drop Editor to Plain text Editor.
After you are done with changing the Default Email Editor, you can create a new Campaign/Template and go to its content. You'd now see the Plain Text Editor there.
Under Email Body, you can find the editor's toolbox on the top. Click on the last button there, named, Code View, where you can import an existing HTML content.
After selecting Code view, you will see an existing HTML code there. You can remove this content and copy the code of your existing HTML and paste it.
Once you are done with the copy-paste process, select Next Recipients to complete editing and scheduling the campaign or click on Save Draft and your Template will be saved.