Automated Email Campaigns with Gmail API

Step 01

Problem

Manual email campaigns are slow, inconsistent and don't scale. Sending personalized follow-ups to dozens of contacts takes hours and it's easy to lose track of who received what. Commercial outreach for Silvigon required a systematic approach.

Step 02

Context and constraints

Built as the email outreach engine for Silvigon, an automation and ERP company. The pipeline sends multi-touch campaigns from equipo@silvigon.com with AI-personalized content, Google Sheets contact tracking, and configurable daily limits. The system handles 500+ contacts across multiple sheets.

Role: Full pipeline developer: Gmail API integration, multi-touch campaign orchestration, DeepSeek personalization, Sheets tracking, and rate control.

Step 03

Key decisions

• Gmail API with persistent OAuth: no dependency on paid email marketing services.
• DeepSeek generates each campaign touch with a different angle (intro, value proposition, sector insight, case study, closing).
• Google Sheets as contact database: each row = one contact with company, email, status, current touch, date, and block/respond flags.
• 5 touches per contact with gaps: +0d, +4d, +6d, +7d, +7d for natural pacing across weekdays only.
• Configurable daily limit (25/day) with randomized send spacing (2-5s) to avoid Gmail blocks.
• Automatic response detection: scans inbox for replies and marks contacts as responded + blocked.
• Weekend guard: campaign skips Saturday and Sunday automatically.
• Block/unsubscribe system: contacts can be flagged as blocked (SI/empty column), stopping all future sends.
• Error handling: individual email failures don't stop the batch; rates are tracked per session.

Step 04

Outcomes

• Fully automated 5-touch campaigns with zero manual intervention.
• AI personalization with different approach in each touch, generated by DeepSeek.
• Real-time contact status tracking in Google Sheets with block/respond automation.
• 500+ contacts managed in the database with multi-sheet organization.
• Silvigon brand: sends from equipo@silvigon.com with company signature and branding.

Metrics

• 25 sends/day with randomized 2-5s spacing between each email.
• 5 touches per contact with gaps: 0, +4, +6, +7, +7 days.
• Weekdays only: automatic weekend skip.
• DeepSeek personalization for each campaign touchpoint (max_tokens=500).
• Google Sheets columns A-W: company, emails, status, last contact, touch count, blocked flag.
• Automatic reply detection and contact status update.
• Per-contact tracking: num_contactos (0-5), bloqueado (SI/empty), estado (email_1-5, responded, bounced, discarded).
• Apple Mail/iCloud unsubscribe handling: auto-generated cancellation requests marked as discarded.

Step 05

Learnings and next improvement

Campaign runner → [Read sheets for pending contacts] → [DeepSeek generates email content]
    → [Gmail API sends] → [Update sheet status (touch + date)]
    → [Next day: repeat until 5 touches or contact responds]
                   ↓
        [Auto-detect replies] → [Mark as responded + blocked]

Step 06

Visual resources