Here is an excellent tool to check if your IP or domain is on a spam blacklist (a.k.a. RBL):
Category: Spam/Antispam
How to Check Spam Blacklists (RBLs)
article #241, updated 11 hours ago
Use DMARC to harden SPF and DKIM
article #1255, updated 139 days ago
The following TXT record:
v=DMARC1; p=reject; pct=100; adkim=s; aspf=s
at least theoretically, should harden SPF and, if present, DKIM. “=s” means “strict”. According to DMARC documentation, DMARC can be used without DKIM, and experiences with a first setup of the above without DKIM are playing out well so far.
Some info is here: