Email deliverability is the ability to reach a recipient’s inbox rather than spam. Delivery only means the receiving server accepted a message. To diagnose problems, separate bounces from inbox placement, verify authentication, review consent and complaints, and compare results by mailbox provider. No sending platform can guarantee primary-tab placement.

Last updated: 15 September 2026

Delivery and deliverability measure different things

A delivery report records acceptance or rejection by the receiving server. An accepted message can still go to spam. Gmail’s Promotions tab is part of the inbox, not a delivery failure. Open rates cannot prove inbox placement because image blocking and privacy features affect tracking.

For teams planning email marketing for small business, start with the audience and the messages people requested. A large contact database is not evidence that everyone has consented to marketing.

There is no universal good deliverability percentage. The January 2023 EmailTooltester test is historical evidence from a particular test setup, not a current benchmark or a promise for your account. Measure your own acceptance, complaints and placement trends before setting alerts.

Why marketing and transactional messages need different monitoring

A missed promotion can reduce campaign response. A delayed password reset can prevent someone accessing an account. Separate these message streams in your reporting and escalation process. Do not add promotional content to an operational message simply to avoid marketing controls.

Make consent, suppression and sender health part of your email marketing strategy. Marketing owns audience relevance; technical owners investigate authentication and server errors. Agree who can pause a send when complaints or rejections rise.

Diagnose a deliverability problem in order

1. Identify the symptom. Is the message rejected, delayed, accepted into spam, or accepted but not opened? Collect timestamps, recipient domains and server responses. Do not retry hard-bounced addresses.
2. Check sender authentication. Test actual received messages, not DNS records alone. Confirm that the sending service uses your approved domain configuration.
3. Inspect consent and suppression. Exclude unsubscribes, complaints and invalid addresses. Investigate where affected contacts entered the list.
4. Compare mailbox providers and cohorts. A problem affecting one provider or an old import needs a different response from a system-wide failure.
5. Reduce risky traffic. Pause the affected campaign or audience while investigating. Resume cautiously with recipients who asked for the message; monitor errors before increasing volume.

Google’s sender guidelines cover authentication, unsubscribe requirements, consent and sending patterns for personal Gmail accounts. Follow the requirements that apply to your sender volume and message type. Google explicitly says it cannot guarantee a provider’s messages will pass its spam filters.

What SPF, DKIM and DMARC actually do

• SPF checks whether the sending server is authorized for the envelope sender domain. It does not authenticate every visible field in a message.
• DKIM uses a cryptographic signature to verify signed message content and the signing domain. It does not certify that the message is wanted or harmless.
• DMARC requires alignment between the visible From domain and a passing SPF or DKIM identity. It also lets domain owners publish a handling policy and receive reports.

Amazon SES documentation explains DMARC alignment. Inventory legitimate senders before tightening an enforcement policy. Authentication helps receivers evaluate identity; it does not guarantee delivery, prevent every phishing attack or determine sending throughput.

Choose tools for the problem you need to investigate

Mailtrap Email API is a sending option to evaluate for application email. Check the current plan’s logs, retention and authentication setup against your troubleshooting needs rather than relying on old throughput figures.

CampaignHQ is a customer retention automation platform for email + WhatsApp, a Meta Tech Partner, and built on AWS. Ask the team to demonstrate suppression handling, reporting and the sending setup for your workload. These capabilities do not override mailbox-provider filtering.

Brevo and SendGrid are other providers to assess. Verify how each exposes bounces, complaints, authentication failures and support escalation. Do not assume a provider automatically removes every inactive contact.

Mailchimp can be evaluated for campaign workflows alongside your email automation needs. Mailjet is another option. Compare current documentation and a controlled test using your own permission-based audience; there is no universally best provider for inbox placement.

When the problem is choosing a platform rather than diagnosing a failed send, use our email service providers in India comparison to assess workflow fit, support and migration requirements.

Keep a practical sender-health checklist

• Keep unsubscribe controls clear and apply suppressions across every relevant marketing workflow.
• Use recognizable sender names and accurate subject lines. A single promotional word is not a universal spam trigger.
• Increase sending volume gradually, particularly after infrastructure changes. Investigate deferrals instead of repeatedly resending.
• Review shared versus dedicated IPs with the provider using actual volume and consistency. A dedicated IP is not automatically better and requires reputation management.
• Use seed tests as a diagnostic sample, not proof of where every subscriber’s message landed.

Start the next review with one affected campaign, its server responses and its consent history. Fix the demonstrated cause before changing tools.

Frequently asked questions

Is Promotions the same as spam?

No. Promotions is an inbox category in Gmail. Do not label it a failed delivery or promise that a sender can force marketing email into the Primary tab.

What should I investigate first when messages bounce?

Read the receiving server’s error code and identify whether the failure is permanent or temporary. Check the recipient, sending limits and authentication before deciding whether a retry is appropriate.

Does authentication guarantee inbox placement?

No. SPF, DKIM and DMARC establish identity signals. Consent, sender reputation, content and the receiver’s filtering still matter.

Should I delete every contact who has not opened?

No. Opens are an imperfect signal. Use consent, clicks, purchases and expected message frequency to define a suppression or re-engagement policy. Never send again to an unsubscribed contact.

When should I change email providers?

Consider switching when the current provider cannot support the reporting, suppression, authentication or operational response you need. Correct audience and consent problems first; a migration will not erase them.

Written by CampaignHQ Team