Measure, monitor, and improve how quickly your emails reach recipient inboxes
Gain insights into email delivery performance and ensure your messages arrive promptly
Learn About TTI | See Forward Email's TTI
Time to Inbox (TTI) is a critical email deliverability metric that measures the time it takes for an email to travel from the sender's server to the recipient's inbox. This metric provides valuable insights into email delivery performance and can help identify potential deliverability issues.
According to Postmark, a leading email service provider, "Time to Inbox is the length of time it takes from when an email is sent from a client until it is logged as delivered." [1]
Unlike other email metrics that focus on recipient engagement (opens, clicks), TTI focuses on the technical aspects of email delivery, helping you understand if your emails are being delivered promptly or experiencing delays in the delivery pipeline.
In today's fast-paced digital environment, the timing of email delivery can significantly impact the effectiveness of your email communications:
- Time-sensitive communications like password resets, verification codes, and urgent notifications need to arrive quickly
- Marketing campaigns timed for specific events lose effectiveness if delayed
- Transactional emails such as order confirmations and receipts should arrive promptly to reduce customer anxiety
- System notifications for critical events need immediate delivery to enable timely responses
Identify and resolve delivery bottlenecks to ensure emails reach inboxes faster and more reliably.
Provide a better experience for recipients by ensuring time-sensitive communications arrive promptly.
Improve open and click-through rates by delivering emails when recipients are most likely to engage.
Compare email service providers based on actual delivery performance to make informed decisions.
Detect delivery problems before they impact your communication strategy or business operations.
Fine-tune your email infrastructure and sending practices based on concrete delivery metrics.
While Time to Inbox (TTI) is a crucial metric for measuring email delivery performance, it's part of a broader set of deliverability metrics that provide a comprehensive view of your email program's health:
The time it takes for an email to travel from the sender's server to the recipient's inbox, measured in seconds or milliseconds. Importance: ★★★★★
The percentage of emails that successfully reach recipients' inboxes rather than spam folders or being blocked entirely. Importance: ★★★★★
The percentage of emails that were successfully delivered to recipients' mail servers (not necessarily inboxes). Importance: ★★★★☆
The percentage of emails that were rejected by recipient mail servers, including both hard and soft bounces. Importance: ★★★★☆
The percentage of delivered emails that recipients mark as spam, a critical factor affecting sender reputation. Importance: ★★★★★
The percentage of delivered emails that recipients open, providing insight into subject line effectiveness and inbox placement. Importance: ★★★☆☆
Forward Email is committed to transparency in email deliverability, providing real-time Time to Inbox (TTI) metrics that demonstrate their exceptional delivery performance. As the only email service with 100% open-source and transparent monitoring, Forward Email sets the standard for deliverability transparency. [2]
Forward Email continuously monitors how long it takes for emails sent through their service to be delivered to test inboxes at major email service providers. Their engineering team is automatically alerted if any delivery times exceed 10 seconds, ensuring consistent performance.
Current Time to Inbox metrics for Forward Email based on their monitoring data:
| Email Service Provider | Average TTI | Data Source |
|---|---|---|
| Forward Email | 1.6s - 1.7s | Forward Email Monitoring [2] |
| Postmark | 11.96s - 23.23s | Postmark TTI Monitoring [1] |
| SendGrid | Inbox placement: 61.0% | Mailtrap Research [3] |
| Mailgun | Inbox placement: 71.4% | Mailtrap Research [3] |
| Amazon SES | Inbox placement: 77.1% | Mailtrap Research [3] |
Note: TTI measurements can vary based on testing methodology, recipient email providers, and network conditions. The data above represents published metrics from each provider's own monitoring or independent research.
Your sender reputation significantly impacts how quickly emails are processed. Email service providers prioritize delivery from senders with established positive reputations.
According to Mailtrap research, email service providers only account for about 30% of your email deliverability, with sender practices making up the rest. [3]
The quality and configuration of your email infrastructure, including servers, IP addresses, and authentication protocols (SPF, DKIM, DMARC), directly affect delivery speed.
Sending large volumes of email simultaneously can trigger rate limiting or throttling by recipient servers, increasing delivery time.
Emails with spam-like content, excessive images, or poor HTML structure may undergo additional filtering, delaying inbox placement.
Different email providers implement varying levels of filtering and processing. Gmail, Outlook, Yahoo, and others each have unique delivery characteristics.
Properly authenticated emails with valid SPF, DKIM, and DMARC records typically experience faster delivery times than unauthenticated messages.
Create test email accounts across major providers (Gmail, Outlook, Yahoo, etc.) to serve as monitoring endpoints.
Add unique identifiers to test emails and implement server-side logging to record send and delivery timestamps.
Collect initial data to establish baseline TTI metrics for different recipient providers and message types.
Configure alerting thresholds to notify your team when TTI exceeds acceptable limits.
Schedule regular test sends to continuously monitor TTI performance and detect trends or issues.
Forward Email handles TTI monitoring automatically for all customers, with transparent reporting and proactive alerts if delivery times exceed thresholds.
Learn More About Forward Email
Users waiting for password reset links expect near-instant delivery. Optimizing TTI ensures users can quickly regain access to their accounts without frustration.
Alerts about security incidents, system outages, or critical updates need to reach recipients promptly to enable timely action.
Order confirmations, shipping notifications, and payment receipts should arrive quickly to reduce customer anxiety and support inquiries.
Authentication codes sent via email must arrive within seconds to provide a seamless login experience without disrupting the user's workflow.
Reminders for upcoming events or appointments should arrive with sufficient lead time to allow recipients to prepare or reschedule if necessary.
IT teams rely on prompt delivery of system alerts to address issues before they impact users or business operations.
Forward Email provides industry-leading Time to Inbox performance with transparent monitoring and reporting. Experience the difference that fast, reliable email delivery can make for your business.
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- Postmark. (2025). Time to Inbox. Retrieved April 6, 2025, from https://tti.postmarkapp.com/
- Forward Email. (2025). Time to Inbox. Retrieved April 6, 2025, from Forward Email's Time to Inbox monitoring page.
- Bostogannashvili, K., Kaitaz, D., & Hurchenko, Y. (2025, January 6). Email Deliverability Comparison Results [2025]. Mailtrap. Retrieved April 6, 2025, from https://mailtrap.io/blog/email-deliverability-comparison/