gmail and outlook run invisible pre-send checkpoints before your email reaches anyone.
the first checkpoint: authentication. SPF, DKIM, DMARC. if these aren't configured properly, you're flagged before your email is even read.
this is the #1 preventable deliverability killer. and most agencies skip it or misconfigure it.
SPF (Sender Policy Framework)
→ tells receiving servers which IPs are authorised to send email from your domain
→ without it: anyone can spoof your domain. servers treat your emails as suspicious.
DKIM (DomainKeys Identified Mail)
→ adds a digital signature to every email you send
→ without it: servers can't verify the email actually came from you. trust score drops.
DMARC (Domain-based Message Authentication)
→ tells servers what to do when SPF or DKIM fails (quarantine, reject, or nothing)
→ without it: you have no policy. servers make their own decision. usually that decision is spam.