storage
The Total Storage limit for a personal account for email is 1TB. I just want you to:-
1.) Launch your Cloud Storage.
2.) Let user use their email storage (1TB) not only for email but also for storage on cloud (Don't expand storage or give separate storage)
3.) Integrate with Dropbox, Google Drive and/or One Drive, such smoothly that users on your cloud storage platform can benefit from their support for different file types & protocol.
4.) Let users use your cloud storage platform through Google Drive, Dropbox, and/or One Drive and can benefit from their support for different file types & protocol.
5.) Do point no.(3 & 4) till you make a good user interface for your email, cloud storage, notes, calendar.
6.) Please make a good Graphical User Interface (GUI) because your exiting interface for email is worse than gmail or outlook, so make it competitive.
7.) You can take take help from LIBRE OFFICE for support of editing in Cloud storage and Notes.
[Extra tip:-
1. I know that your users have declined rapidly, thanks to google and microsoft but this for your support and give your existing infrastructure and resources to your loyal users, so that more-&-more users can be loya to you as well.
2. Remember how Brave browser had done marketing regarding youtube ads on (other browser vs brave browser), use same technique and market your cloud storage like:- other popular email/drive(cloud storage) providers total storage is 15gb or 5gb or any other vs yahoo, where it is 1000GB)
3. You can uprade your security too and use it in your marketing like proton mail.]
Lastly, Integrate your Email, Cloud Storage, Calendar and Notes, as smoothly as possible. Total storage (including all serives) should be well under what you can afford for all of your users.
Now, I've told you many things to do,If possible do all of it in your free version with ads and make some premium versions for removing ads and some special features ( special one, not any feature that you can get for free in other platform ).
Do what you can & leave what you can't because it is simply a suggesion or product feedback.
THANK YOU.

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Roushan Kumar commented
I want this to happen and Yahoo to come into market & play agian.