Most of my mail is not forwarded to my new address

Most of my mail is not forwarded to my new address

When my inbox got frozen (I did not exceed my daily quota, but apparently using an email client like Thunderbird arbitrarily increases your outgoing flow, which I don't understand but find too annoying for me to keep using Zoho), I decided to switch to another email client.
The problem is that the forwarding function does not send all of my mail to my new address.

How is that? How can I fix this?

Thank you for your help