Hello Felicia Okai,
Good day!
I hope this message finds you well. I'm so sorry to hear that you're experiencing frustration with the auto-correct feature in the new Outlook editor. Specifically, you're having trouble getting the word "i" to capitalize correctly.
Issue Summary:
- The auto-correct feature in the new Outlook editor is not capitalizing the word "i" correctly.
- You're unable to add the word "i" to the editor's dictionary to correct the issue.
- This problem has been ongoing for a year, and you're looking for a solution.
I apologize for the inconvenience this is causing you. I understand how frustrating it can be to have a simple issue like this persist for so long.
I have tested your issue from my end and I realized what you were describing is very true. The New Outlook has undergone several changes, and some features from the Classic Outlook might not be functioning the same way. The auto-capitalize feature, which is part of the Editor settings, might not be working as expected due to these changes.
I have submitted your feedback and voted, and I've also shared this link with my team for voting. Your detailed information about this issue will be very helpful for Outlook product development! Thanks in advance for this!
Feedback link: Auto-Capitalize Feature Not Working Correctly for the Word "I" · Community

In the meantime, I humbly request you to submit vote on the thread which contains the feedback like so others with this similar issue can locate it and vote on the link easily as well. In this way, our support engineers will be able to collate data and support details about this and resolve the issue as quickly as possible.
Thank you very much for your understanding!
We look forward to hearing from you! Thank you for your time. Have a good day!
Sincerely,
Eleni | Microsoft Community Moderator