Glossary
What is email deliverability?
Whether your emails land in the inbox instead of spam or getting blocked, based on authentication, reputation and list quality.
Definition
Email deliverability is the ability of your emails to reach the recipient's inbox rather than the spam folder or being blocked. It depends on sender authentication, your domain's reputation, list quality, spam complaints and content, and each mailbox provider, such as Gmail, Yahoo or Outlook, judges it separately.
Delivery vs deliverability
Delivery means the receiving server accepted your email instead of bouncing it. Deliverability is where it went next: the inbox, a promotions tab or spam. An email can be "delivered" and still never be seen, which is why a 99% delivery rate in a dashboard doesn't mean people are reading your mail.
What affects deliverability
- Authentication. SPF, DKIM and DMARC prove the mail really comes from your domain.
- Spam complaints. Google's sender guidelines say to keep the spam rate shown in Postmaster Tools below 0.10% and to avoid ever reaching 0.30%. Yahoo asks bulk senders to stay below 0.3%.
- List quality. Sending to invalid addresses raises your bounce rate.
- Engagement. Replies and opens help; deletes without reading don't.
- Sending patterns. Sudden jumps in volume from a new domain look suspicious.
How to check it
Set up Google Postmaster Tools for your domain to see spam rate and reputation for Gmail. Send test emails to your own Gmail, Outlook and Yahoo addresses and see where they land. Watch for a sudden drop in replies on a sequence that used to work, which is often the first sign of a spam-folder problem. Open the full headers of a test email to confirm SPF, DKIM and DMARC show "pass", and review your sending tool's bounce and complaint reports.
Common mistakes
- Cold emailing from your main company domain with no warm-up.
- Buying lists and sending without verification.
- Heavy images, many links or link shorteners in plain sales emails.
- Missing or broken authentication records after adding a new sending tool.
- Keeping addresses that hard-bounced on your list.
How Siela AI uses it
Siela verifies email addresses before sending outreach, and sends from your own accounts within daily goals you set.
Questions
What is a good email deliverability rate?
Aim for most of your mail to land in the inbox, and watch the signals mailbox providers publish. Google says to keep the spam rate in Postmaster Tools below 0.10% and never reach 0.30%, and Yahoo asks bulk senders to stay under 0.3%. Inbox placement itself varies by tool and test method.
Why are my emails going to spam?
Common causes are missing or broken SPF, DKIM or DMARC records, a new or low-reputation domain, high spam complaints, sending to invalid or bought addresses, sudden volume spikes and spam-like content. Check authentication first, then list quality, then sending volume and content.
Sources, checked 25 October 2026: Google: Email sender guidelines, Yahoo: Sender best practices.
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