Over 1000 emails per day

1. it is difficult to give an objective answer here - because if you send out a mailing list with contacts among which there are contacts who did not agree to the mailing list, you will be banned.
2. if you send out mailings to unverified databases - you bought them on the Internet and there are fake, spam and suspicious addresses among the addresses - you will be banned.
3. if your mail domain allows you to send 1k letters per day - boxing will send them - if not, then no.
as an option, you can use the mailing list via sendpulse - it is quite adequate for the price list and there is all the required functionality.
but see the points above - if you do not fulfill p1 and p2 - 99% of services will ban you for spam

I did not see the answer to the question "And see if the letter reached, whether the addressee opened the letter"

there is no such functionality in boxing - but this functionality is in the service about which it is written above

But then it will be necessary to constantly switch to that service and look at the statistics
In addition to the sendpulse in synchronization with which service, are there statistics on deliveries and openings?