If you have necessity to check if your email/SMTP Server, or domain, is blocked by some antispam here they are some websites that might be useful for this check purposes.
Website Blacklist Checker
https://sitechecker.pro/blacklist-checker/
Blacklist Check
https://mxtoolbox.com/blacklists.aspx
Email Health
https://mxtoolbox.com/emailhealth
SpamHaus
https://check.spamhaus.org/not_listed/?searchterm=ruffino.it
IP Blacklist & Email Blacklist Check
https://dnschecker.org/ip-blacklist-checker.php
Antiabuse project
http://www.anti-abuse.org/multi-rbl-check/
[update 2022.05.09]
You can send, your email, to a specific address to understand it it has some spam related problems
https://www.emailchecky.com/en/
[update 2022.05.26]
https://talosintelligence.com/
[update 2022.05.27]
If you need to verify DNS propagation here it is an useful website:
https://dnschecker.org/#TXT/_dmarc.ruffino.it