Email Warmup

Email Warmup

Warmup is the process of gradually building sender reputation for new email accounts before using them in campaigns. Without warmup, new accounts sending cold emails risk landing in spam or getting blocked.

How Warmup Works

When warmup is enabled on an email account, it joins the warmup pool — a network of all warmup-enabled accounts (both user accounts and dedicated pool accounts). These accounts send realistic-looking emails to each other, simulating natural email activity.

The warmup cycle runs automatically on the VPS in two phases:

Phase 1 — Sending: The system pairs accounts from the pool and sends warmup emails between them. Pairing logic:

• Accounts are randomly selected from those that haven't reached their daily target
• 70% preference for cross-provider pairing (e.g., Google Workspace → Microsoft 365) to build reputation across different email providers
• Random delays of 5-30 seconds between each send to appear natural
• Each email gets a hidden [WU-key] tag at the bottom for identification
• Custom X-Warmup-Email header added for programmatic detection
• Emails are saved to the sender's Sent folder via IMAP

Phase 2 — Processing Incoming: For each account in the pool, the system connects via IMAP and:

1. Spam Rescue: Checks the Spam/Junk folder for warmup emails. If found, moves them back to Inbox. This trains the email provider that these senders are legitimate.
2. Inbox Processing: Finds warmup emails in the Inbox, marks them as read.
3. Auto-Reply: 70% chance to send an AI-generated reply to each warmup email (not 100%, to look natural). Replies are only sent to emails received in the last 20 minutes to prevent duplicates. Replies to replies are skipped to prevent infinite loops.

Daily Ramp Schedule (User Accounts)

New accounts start slow and gradually increase volume over 30 days:

Pool accounts (already warmed) send a random 10-15 emails per day with no ramp.

AI-Generated Content

Warmup emails are generated by GPT-4o-mini to look like real business correspondence. The system uses 12 conversation scenarios: meeting follow-up, project update, document request, scheduling, professional introduction, feedback request, thank you, quick question, collaboration proposal, event invite, resource sharing, and casual check-in.

Emails are generated in the appropriate language based on the recipient's email domain (e.g., .de → German, .pl → Polish, .sk → Slovak, .cz → Czech). They use professional tone, natural greetings appropriate to each language, and are kept short (2-4 sentences). The AI is instructed to include minor imperfections occasionally to appear human.

If GPT is unavailable, the system falls back to pre-written templates in the appropriate language, covering the same scenarios.

Replies are similarly AI-generated: short (1-3 sentences), matching the formality of the original, with natural acknowledgments.

Delivery Speed Testing

The system can test delivery speed between any two accounts in the pool:

• Sends a test email and polls the recipient's IMAP inbox every 10 seconds
• Categorizes results: Fast (<30s), Normal (<2min), Slow (<5min), Throttled (>5min), Failed
• Throttled results trigger a WARNING health status on the sender account
• Can run across all unique domain pairs in the pool to detect problematic routes

Health Monitoring

• Accounts with 3+ consecutive SMTP/IMAP errors are marked CRITICAL and excluded from the pool
• Successful sends reset the error counter to 0
• Accounts marked CRITICAL are automatically skipped in pairing

Daily Reset

At midnight, all counters reset: sent today, received today, replied today, spam rescued. The warmup day counter increments by 1, and daily targets are recalculated based on the ramp schedule.

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