Deliverability is whether your emails actually reach the inbox. Yahoo requires every sender to keep its spam rate below 0.3% and to authenticate with SPF or DKIM at a minimum, and Gmail asks senders to stay below 0.10% in Postmaster Tools and never reach 0.30%. Even great copy fails if it lands in spam. This guide covers the levers that move deliverability, and the OutreachBox features behind each.
Quick answer: To land in the inbox, warm up new email accounts before sending, verify your contact list to remove invalid addresses, personalize and segment your emails, send to engaged contacts, and continuously remove bounces and unsubscribes. OutreachBox's warmup, verification, and analytics features support each of these.
Before you start
Have access to your domain DNS, sender settings, and recent bounce responses. Separate delivery failures from low engagement.
Practical example
If a campaign starts bouncing, pause expansion, inspect the bounce codes, and recheck the list. Authentication errors call for a DNS fix; invalid recipients call for better data hygiene.
Check your result
A delivered status means the receiving server accepted a message; it does not prove inbox placement. Warmup and content edits cannot guarantee that every recipient will see it.
The deliverability checklist
- Authenticate the domain. Confirm SPF, DKIM, and DMARC with the free SPF, DKIM, and DMARC checker. The standards are RFC 7208 (SPF), RFC 6376 (DKIM) and RFC 9989 (DMARC).
- Warm up your sending account. Start around 5–10 emails per day per new inbox during warmup, ramp gradually, and keep roughly 20–50 per warmed inbox after warmup. OutreachBox warmup itself sends a fixed 10 emails per day. See How to Warm Up an Email Account.
- Verify your contacts. Emailing invalid addresses spikes bounces and hurts reputation. See How to Verify Email Addresses in Bulk.
- Keep your list clean. Remove bounced and unsubscribed contacts regularly. See How to Clean Your Email List.
- Segment and personalize. Relevant emails to the right people get more engagement and fewer spam complaints.
- Send to engaged contacts. Engagement (opens, replies) signals trust to mailbox providers.
- Monitor metrics. Watch bounce rates, open rates, and spam scores and act on them.
How to diagnose deliverability problems
| Symptom | Likely cause | Fix |
|---|---|---|
| High bounce rate | Unverified or stale list | Verify and clean the list |
| Low open rate | Spam folder placement or weak subject | Improve warmup, subjects, and timing |
| Rising unsubscribes | Poor targeting or frequency | Segment better, reduce frequency |
| Account flagged | Sending too much, too fast | Slow down; rely on warmup |
Best practices
- Never send a cold campaign from a brand-new, un-warmed account.
- Verify every imported list before the first send.
- Personalize with variables and segment by group, status, or verification quality.
- Maintain a steady, gradual sending volume rather than sudden spikes.
- Review campaign analytics after every send and prune your list.
Sources
- Yahoo, "Sender Best Practices"
- Google, "Email sender guidelines"
- IETF, "RFC 7208: Sender Policy Framework (SPF) for Authorizing Use of Domains in Email, Version 1"
- IETF, "RFC 6376: DomainKeys Identified Mail (DKIM) Signatures"
- IETF, "RFC 9989: Domain-Based Message Authentication, Reporting, and Conformance (DMARC)"
Checked October 26, 2026.
Frequently Asked Questions
Why are my emails going to spam?
Common causes are an un-warmed account, an unverified or stale contact list, low engagement, or sending too much too quickly. Warm up, verify, and segment. Start around 5–10 emails per day per new inbox during warmup, ramp gradually, and keep roughly 20–50 per warmed inbox after warmup.
How do I lower my bounce rate?
Verify email addresses before sending and remove invalid and bounced contacts. See How to Verify Email Addresses in Bulk.
Does personalization affect deliverability?
Yes — personalized, relevant emails earn more engagement and fewer spam complaints, which improves your sender reputation over time.
Related articles
- SPF, DKIM, and DMARC checker
- How to Warm Up an Email Account
- How to Verify Email Addresses in Bulk
- How to Clean Your Email List
Deliverability is earned: warm up, verify, personalize, and keep your list clean.