priyanka123 Have you tried using PrettyMail ?
What is also possible is to override some files of the Backend. I did this for translating E-Mails like the ones that are sent when there is a new post on a discussion that a user subscribed to. Basically you can add this to the composer.json of your extension:
"autoload": {
"psr-4": {
"My\\Extension\\": "src/"
},
"files": [
"src/Overrides/Notification/NewPostBlueprint.php",
]
}
That way you can basically change anything you like. Maybe take a look at the source code of PrettyMail to see how it does send HTML enabled e-mails.
