rahul how far are you already in your setup? Are you using discussions or replies to store applications? Or something else?
If you create one discussion per application, or want to store applications completely separately then my paid Formulaire extension could be of use. You could create a custom form, optionally mark it as a discussion form, and configure an email to be sent to the user when the form is submitted. One potential benefit could also be that this method allows new discussions to be created in a tag the author cannot see.
I'm not sure how you would connect offers to applications though. With Formulaire and the standalone froms, you could have one form per offer, then form submissions would be applications.
For discussion forms you would have to use tags or taxonomies to categorize the submissions.
I am planning to add reply/comment fields in the future, but I'm not sure I will be able to ship that feature this year.
If you want to use "vanilla" discussions for your use case and send an email when a user replies or creates a discussion in a tag, you could use the PHP extension API to hook into the Started or Replied events and then send an email using the mailer instance. You can send raw text or call a blade view to be used as template. This is not very complex, but I'm not sure we have any example available to copy-paste.
Maybe you could use the webhook extension then write the email logic using an external server.
