I met the same problem as you these days, and now it has been solved.

The reason is that there is an I/O port conflict between foxmail and Yahoo.

The solution is:

Log in to foxmail official website:/

Download foxmail 7

This is the latest IMAP mail software, which feels clearer than SMTP.

Then import the old version of foxmail mail, and the working data will not be affected at all.

I hope the above suggestions will help you.