Disable email sync outside working hours
FairEmail is a popular open source Email client (crossed 100,000 downloads) which can do this for all accounts (global) but not per account. This is because of maintenance and support of app plus battery consumption.

However, you can still use automation for custom polling to achieve individual account sync (this is a pro feature) 

You can set the day /hour wise schedule



Developer is very active and responsive as you can see from the XDA thread, which is the right place to get your questions answered.

I am an extremely satisfied user of FairEmail and not affiliated anyway with it.