How to Check SPF, DKIM, and DMARC Records in Python

If your app sends email — transactional or marketing — three DNS records decide whether it lands in the inbox or the spam folder: SPF , DKIM , and DMARC . Here's how to look them up and sanity-check them in Python, no third-party API required. Install the one dependency: pip install dnspython SPF: who is allowed to send SPF lives in a TXT record on the domain itself and starts with v=spf1 . import dns.resolver def get_spf ( domain ): for rec in dns . resolver . resolve ( domain , " TXT " ): txt = b "" . join ( rec . strings ). decode () if txt . startswith ( " v=spf1 " ): return txt return None print ( get_spf ( " github.com " )) # v=spf1 ip4:... include:_spf.google.com ~all A quick gotcha worth checking: SPF allows at most 10 DNS-querying mechanisms ( include , a , mx , ptr , exists , redirect ). Go over and receivers return permerror , which quietly breaks authentication: def spf_lookup_count ( spf ): return sum ( spf . count ( m ) for m in ( " include: " , " a: " , " mx: " , " ptr " , " exists: " , " redirect= " )) spf = get_spf ( " example.com " ) if spf and spf_lookup_count ( spf ) > 10 : print ( " ⚠️ SPF exceeds the 10-lookup limit " ) DMARC: the policy that ties it together DMARC is a TXT record on the _dmarc. subdomain and starts with v=DMARC1 . def get_dmarc ( domain ): try : for rec in dns . resolver . resolve ( f " _dmarc. { domain } " , " TXT " ): txt = b "" . join ( rec . strings ). decode () if txt . startswith ( " v=DMARC1 " ): return dict ( kv . strip (). split ( " = " , 1 ) for kv in txt . split ( " ; " ) if " = " in kv ) except dns . resolver . NXDOMAIN : return None print ( get_dmarc ( " github.com " )) # {'v': 'DMARC1', 'p': 'reject', 'rua': 'mailto:...'} The key field is p : none (monitor only), quarantine (spam folder), or reject (bounce). If a domain sends real mail but has p=none , it's not protected against spoofing yet. DKIM: the signature key DKIM is trickier because you need the selector — a label chosen by the sender that lives at SELECT