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Follow-up Sequences

Sequences define automated follow-up emails that trigger based on recipient behavior. Use them to send reminders, additional value, or alternative approaches.

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How Sequences Work

When a recipient doesn’t take the expected action, ColdSend automatically sends the follow-up email:
  1. Initial email is sent to the lead
  2. ColdSend waits the specified number of days
  3. If the trigger condition is met, the follow-up is sent
  4. Process repeats for subsequent sequences

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Creating Sequences

Add sequences when updating a campaign: 
requests.put(
    f"{base_url}/api/public/v1/campaigns/{campaign_id}",
    headers={"X-API-Key": api_key},
    json={
        "sequences": [
            {
                "step_number": 2,
                "trigger_type": "NOT_OPENED",
                "wait_days": 3,
                "variants": [
                    {
                        "variant_name": "A",
                        "subject_template": "Following up on my previous email",
                        "email_content": "Hi {{first_name}},\n\nI wanted to follow up on my previous email...\n\nBest,\nJohn",
                        "distribution_percent": 100
                    }
                ]
            },
            {
                "step_number": 3,
                "trigger_type": "NOT_REPLIED",
                "wait_days": 5,
                "variants": [
                    {
                        "variant_name": "A",
                        "subject_template": "Last thought",
                        "email_content": "Hi {{first_name}},\n\nOne last thought I wanted to share...\n\nBest,\nJohn",
                        "distribution_percent": 100
                    }
                ]
            }
        ]
    }
)

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Sequence Fields

FieldTypeRequiredDescription
step_numberintegerYesSequence position (2-4)
trigger_typestringYesTrigger condition
wait_daysintegerYesDays to wait (1-30)
enable_unsubscribebooleanNoOverride campaign setting
variantsarrayYesEmail variants for this sequence

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Trigger Types

TriggerDescription
NOT_OPENEDSend if the previous email was not opened
NOT_REPLIEDSend if the previous email was not replied to
OPENED_BUT_NOT_REPLIEDSend if opened but not replied

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Trigger Behavior

NOT_OPENED
  • Triggered when the recipient has not opened any previous email
  • Useful for re-engaging unresponsive leads
NOT_REPLIED
  • Triggered when the recipient has not replied to any email
  • Includes recipients who opened but didn’t respond
  • Most commonly used trigger
OPENED_BUT_NOT_REPLIED
  • Triggered only when the recipient opened an email but didn’t reply
  • Useful for re-engaging interested prospects
  • Skips recipients who didn’t open at all

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Sequence Limits

LimitValue
Maximum sequences3 per campaign
Step numbers2, 3, or 4
Wait days per sequence1-30 days
Total sequence duration45 days maximum

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Step Numbering

  • Step 1 is always the initial email (defined in variants)
  • Sequences start at step 2
  • Steps must be sequential (2, 3, 4)

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Duration Calculation

Total sequence duration is the sum of all wait_days: 
Sequence 2: 3 days
Sequence 3: 5 days
Sequence 4: 7 days
Total: 15 days

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Sequence Variants

Each sequence can have its own variants for testing: 
{
    "step_number": 2,
    "trigger_type": "NOT_OPENED",
    "wait_days": 3,
    "variants": [
        {
            "variant_name": "A",
            "subject_template": "Did you see this?",
            "email_content": "...",
            "distribution_percent": 50
        },
        {
            "variant_name": "B",
            "subject_template": "Thought you might have missed this",
            "email_content": "...",
            "distribution_percent": 50
        }
    ]
}
Leads retain their variant assignment from the initial email. Sequence variants apply only if you want to test different follow-up approaches.

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Best Practices

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Timing

Follow-upRecommended Wait
First follow-up2-4 days
Second follow-up5-7 days
Final follow-up7-10 days

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Content Strategy

First Follow-up (Step 2)
  • Reference the original email
  • Add a small piece of value
  • Keep it brief
Second Follow-up (Step 3)
  • Offer something specific (case study, resource)
  • Use a different angle
Third Follow-up (Step 4)
  • Create urgency or finality
  • Consider a “breakup” email

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Subject Lines

Follow-up subject lines can:
  • Reference the previous subject: "Re: Quick question about {{company}}"
  • Use a fresh approach: "One more thing about {{company}}"
  • Create curiosity: "Did you see this?"

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Validation Errors

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Invalid Step Number

{
  "detail": "step_number must be 2, 3, or 4"
}

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Non-Sequential Steps

{
  "detail": "Sequences must be sequential. Missing step: 3"
}

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Duration Exceeded

{
  "detail": "Total sequence duration cannot exceed 45 days"
}