Privacy Policy

1. Introduction

Welcome to smtp-sync. We operate as a "Stateful Proxy" utility designed to bridge your legacy email accounts (POP3/IMAP) securely to your Gmail "Command Center". This Privacy Policy outlines how we handle your data, with a strong commitment to a Zero-Trust security model.

2. Data Collection & Authorization

To provide our services, we collect and securely store the following information:

• Google OAuth 2.0 Tokens: We store refresh tokens used exclusively to authorize the users.messages.import API. These tokens allow us to push emails to your Gmail inbox and are managed via Google's secure OAuth 2.0 flow.
• Mailbox Credentials: The usernames and passwords for your source POP3/IMAP servers. These are required to establish the synchronization connection.

3. Data Protection Mechanisms

We take the security of your sensitive data seriously and implement the following protection mechanisms:

• Encryption at Rest: All sensitive credentials, including your legacy mailbox passwords and Google OAuth tokens, are encrypted at rest using industry-standard AES-256 encryption.
• Encryption in Transit: All data transfers between our servers, your legacy email providers, and Google APIs are conducted over secure TLS (Transport Layer Security) encrypted connections.
• Data Isolation and Access: Operational credentials are isolated from the analytics system and are available only to the synchronization processes that require them. Authorized personnel may access the separate analytics system through Metabase to measure registration, onboarding, mailbox connection, and service access activity, and to investigate service reliability or security issues.

4. Zero-Trust Data Processing

Our architecture is built on a "No-Storage" binary streaming model. We believe that your email content is your own.

• No Content Persistence: Email bodies, attachments, and content are never persisted to our disks or databases.
• In-Memory Streaming: Our high-concurrency workers stream data directly from your source server to the Gmail API using temporary in-memory buffers that are cleared immediately after the transfer.

5. Data Retention & Deletion

We adhere to strict data retention policies to ensure you have full control over your information:

• Retention Period: We retain your mailbox credentials and sync metadata only for as long as your synchronization task remains active in our system.
• User-Initiated Deletion: You can delete mailbox connections through the dashboard. The dashboard does not currently provide account deletion. To request account or analytics data erasure, email hello@mailtogmail.com.
• Operational Data Wiping: Upon deletion of a mailbox connection, its operational credentials and active synchronization state, including encrypted passwords and OAuth tokens, are immediately and permanently removed from our active operational databases. The analytics records described below remain unless a verified erasure request applies.
• Google User Data: If you revoke access via your Google Security settings or delete a mailbox connection, the associated Google OAuth tokens and operational mailbox connection metadata are removed from our active operational databases. Historical service analytics remain under the retention and erasure terms below.
• Service Analytics: We retain account email addresses, registration timestamps, session creation timestamps, IP addresses, and browser User Agent strings in our PostgreSQL analytics database without an automatic expiration period. This historical data is used to measure registration, onboarding, mailbox connection, and service access activity, and may remain after an operational account is deleted unless a verified erasure request applies.
• Erasure Requests: Before acting on an account or analytics erasure request, we verify the requester's identity to protect users from unauthorized deletion. After verification, we delete or irreversibly anonymize the requester's email address, IP addresses, browser User Agent strings, and other user-linked analytics. We may retain information when required by law or needed to establish, exercise, or defend legal claims. Deleted data may also remain temporarily in secured backups until those backups expire or are overwritten, and will not be restored to active use.
• Temporary Event Queue: Cloudflare D1 keeps acknowledged copies of session creation events until they are older than 30 days, when they become eligible for cleanup. They may remain longer if synchronization or cleanup is delayed or not running. Events that have not been successfully transferred to PostgreSQL are not automatically deleted. For a verified erasure request, event rows may be irreversibly anonymized in place rather than deleted when retaining their numeric sequence is required to keep the synchronization log complete.

6. Glass Box Audit (Metadata Logging)

To ensure high reliability and to give you full transparency into the health of your sync connections, we maintain a "Glass Box Audit" trail.

• What is Logged: We log only sync metadata, which includes timestamps, sender domains, delivery status, and message sizes.
• Analytics Metadata: Operational logs do not contain email content or authentication secrets. The separate analytics database stores the account and session metadata described in Section 5, including email address, IP address, and User Agent.
• Operational Logs: The dashboard lets you view operational synchronization history for your own mailbox connections. It does not expose every metadata or analytics record associated with your account.
• Internal Analytics: The separate account and session analytics described in Section 5 are available only to authorized personnel through Metabase for the stated analytics, reliability, and security purposes.

7. Third-Party Services

We utilize trusted third-party infrastructure to deliver our service:

• Google Cloud (Gmail API): For delivering synchronized mail.
• Mailjet: For sending system notifications and error alerts.
• Stripe: For secure billing and subscription management.
• Neon.com: For metadata ingestion and dashboard visualization.
• Fly.io & Cloudflare: For dedicated hardware and network security.

8. Google API Disclosure

Our use and transfer to any other app of information received from Google APIs will adhere to Google API Services User Data Policy, including the Limited Use requirements.

We do not use your Gmail data (including message content and metadata) to serve advertisements or for any marketing purposes.

Important: We do not use, sell, or transfer your Gmail data for the purpose of training or improving generalized Artificial Intelligence (AI) or Machine Learning (ML) models.