This new option to block is under the more link next to the reply button for android app and in the dropdown for the web app.
When you block a sender, they will not be notified and all of their future mails will go to Spam folder. Unlike “Report Spam” button which is like “vote for spam” option, this option will permanently block the sender. Technically it will only keep the mail away from your inbox and push it into the spam box. The process is same for PC and the app. For unblocking, you will have to go to Gmail settings, click on “Filters and Blocked Addresses” where you can find the sender and unblock the email address.
Unblocking on android can be done by going to the sender’s mail in the spam folder and under more option you can tap on the unblock option and confirm the action to unblock the sender. This is little complex, so better to find and unblock senders from web app only. Unsubscribe – This option lets you unsubscribe from a bulk mailing service through Gmail itself without going through the trouble of visiting the site or finding that small “unsubscribe” at the bottom on the mail content. For PC – click on the unsubscribe button next to the sender’s email address (as shown) and then Confirm unsubscribe.
For android – Tap on the more option under which you will find the unsubscribe button, tap on it and confirm unsubscribe. However, Unsubscribe link will only appear for the eligible bulk mailing services. Gmail will auto-detect which mails are of no use to you, or have no personalised information or are promotional in nature and only for them the unsubscribe button will appear. These new additions are really worth because it gives the user better control to reject mails without much trouble. The only issue I faced was that for a particular address the unsubscribe option was available on the desktop but not on the app. I have reported the issue and will update about it soon.