One App/platform For Multiple Email Accounts

Good day, all.

I currently have three email accounts I use regularly, two are on Outlook and one is Gmail. I would like to have one web app to access them all. Unfortunately, unlike the Android Outlook app, I can only access two out of the three in any web mode.

New Outlook (outlook for Windows) and Outlook (PWA)

• my university's Outlook account
• my Gmail

https://outlook.live.com/mail/0/ gives me access to

• my university's Outlook account
• Red Cross's Outlook account
• (Microsoft mail using outlook_AE09BBBBA9693DA8@outlook.com which I do not use, but which is confusing because it uses my Gmail address.)

https://outlook.office.com/mail/ gives me access to

• my university's Outlook account
• Red Cross's Outlook account

Does anyone have a recommended app/platform that will allow me access to all three accounts?