Hi @Vaibhav Yeole
Welcome to our forum!
According to your description, even if your users unsubscribe from your emails on Outlook for Web, they will still receive emails from you, and those emails will no longer have an unsubscribe button, right?
Based on my research, after i unsubscribe from an email i subscribed to on Outlook for Web, I can still find the unsubscribe button from other emails in this series. Considering the issue may relate to your application, it is suggested that you contact the developers of the application and have them to check 'unsubscribe feature as per RFC2369-compliant'. Please kindly understand that the Outlook tag here we mainly focus on general issues about Outlook desktop client.
In addition, if the users are using an outlook.com account on Outlook for web, you may contact them to follow the steps (Settings>Mail>Subscriptions>Unsubscribe) to unsubscribe emails send from your application. If this still does not work, i am afraid that you need to contact the users to block your emails from their side, More information: Block senders or mark email as junk in Outlook.com or Outlook on the web. - Microsoft Support.
Hope it helps!
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