Mail interface for a large number of mailboxes?

Question

Mail client

Actually, I'm interested in something like this.
I describe how I imagine it.
On my server there is a software that checks mailboxes at a certain interval and shows new letters.
I am satisfied with using Thunderbird, but I would like similar functionality "from anywhere, anytime, anywhere".
So that you can also write from these boxes.
In general, a full-fledged SMTP client for a large number and different mailboxes, not only Yandex.
PySy: services like Yandex mail or Mail are not suitable, due to the complexity of the settings, constant confirmations, and Yandex limits the number of boxes.
I have over 50 of them.
These are the technical boxes of sites, metrics, counters, webmasters are attached to them, so it is important to be aware of it constantly and promptly.
Redirects are also not needed, because each time you put it or delete it is very tedious.

Answer 1

Found the answer here
In what online mail client is it possible to add several mailboxes (imap i.mail) and read letters from these boxes on one page?
Thanks Nikolay Petyukh