Migrating Suppression Lists (Unsubscribes, Bounces, Complaints)
This guide explains how to migrate suppression lists — including unsubscribed contacts, bounced addresses, and spam complaints — from your previous email platform to Sender.
Before You Start
- Completed subscriber import in Sender
- Verified sending domain in Sender
- Admin access to your source platform to export suppression data
- Separate export files prepared for each suppression type (unsubscribes, hard bounces, spam complaints)
- A dedicated group created in Sender to tag imported suppression contacts (e.g., "Imported – Unsubscribes")
Migrating suppression lists before sending any campaigns from Sender is critical. Failing to do so risks emailing contacts who previously opted out, which damages deliverability and violates compliance requirements.
Audit Your Source Platform
Unsubscribed contacts — Locate your full unsubscribe list in your source platform's audience, suppression, or compliance section. Document the total count of unsubscribed contacts and export them as a .csv file containing at minimum the email address column.
Hard-bounced addresses — Find your bounced contacts list in the source platform's deliverability or suppression area. Export hard bounces separately from soft bounces, as hard bounces represent permanently undeliverable addresses that must be suppressed in Sender.
Spam complaints — Check your source platform's complaint or feedback loop section for contacts who reported your emails as spam. Export these contacts as a separate .csv file. In Sender, spam complaints map to the Reported spam status, but this status is applied automatically by Sender's system and cannot be set manually through import.
Suppression list overlap — A single contact may appear on multiple suppression lists (e.g., unsubscribed and bounced). Before importing, deduplicate across your exported files so each email address appears in only one file, prioritizing the most restrictive status.
Steps to Migrate Suppression Lists
Step 1 — Export suppression data from your source platform
In your source platform, navigate to the suppression or audience management area and export each suppression type as a separate .csv file. Each file needs only an email column, though you may include first_name and last_name if available. Name the files clearly — for example, unsubscribes.csv, hard-bounces.csv, and spam-complaints.csv. Verify each file opens correctly and contains valid email addresses before proceeding.
Step 2 — Import the suppression contacts into Sender
In Sender, go to Subscribers → Add subscribers and select Import from a file. Upload your unsubscribes.csv file. On the Match the columns screen, map the email column to E-mail using the dropdown and skip any unneeded columns. Under Add subscribers to a group, select or create a dedicated group such as "Imported – Unsubscribes" using the Choose groups dropdown. Click Start import. Repeat this process for each suppression file, assigning each to its own clearly named group.
Step 3 — Apply the Unsubscribed status in bulk
After the import completes, go to Subscribers. Use the Groups dropdown filter at the top of the subscriber list to filter by your suppression group (e.g., "Imported – Unsubscribes"). Select all filtered subscribers by clicking the checkbox in the header row, then click Actions → Unsubscribe. This changes their email status from Active to Unsubscribed, preventing Sender from sending campaigns to these contacts. Repeat for your spam complaint group.
Step 4 — Handle bounced addresses
Sender does not allow you to manually set a subscriber's status to Bounced through the dashboard or the standard import process. For hard-bounced addresses, you have two options. You can apply Actions → Unsubscribe to the bounced contacts group to prevent any sends to those addresses. Alternatively, contact Sender support at support@sender.net and request that the bounced status be applied to the contacts in your imported bounce group. The support team can update subscriber statuses in bulk on the backend.
Mapping Reference
Unsubscribed contacts → Unsubscribed status in Sender — Import the contacts as subscribers, assign to a dedicated group, then use Actions → Unsubscribe to set their status. Sender treats unsubscribed contacts as globally unsubscribed across all groups.
Hard bounces → Bounced status in Sender — Sender's Bounced status is typically applied automatically when a send attempt fails. To apply this status to imported addresses, contact Sender support or use Actions → Unsubscribe as a functional equivalent to prevent sends.
Spam complaints → Reported spam status in Sender — The Reported spam status in Sender is assigned automatically through feedback loops and cannot be set manually during import. Apply the Unsubscribed status to imported complaint contacts to ensure they are suppressed from sends.
Non-subscribed status in Sender — This status applies to contacts who were added but never confirmed a subscription. It has no direct equivalent in most source platform exports and is not relevant to suppression list migration.
Source platform tags or lists indicating suppression → Sender groups — If your source platform used tags or list-level unsubscribes to track suppression, map each tag or list to a separate Sender group before importing so you can apply the correct status in bulk.
What Cannot Be Migrated Automatically
Subscriber status via file import — Sender's import tool does not include a Status field in the column mapping step. You cannot set a contact's status to Unsubscribed, Bounced, or Reported spam during the file import. Status changes must be applied after import using bulk actions.
Bounced status via the dashboard — The Bounced status cannot be applied manually through the Sender dashboard. It is assigned automatically when Sender detects a delivery failure. Contact Sender support to apply this status to imported addresses.
Reported spam status — This status is triggered by ISP feedback loops and cannot be assigned manually. Use Unsubscribed as the functional equivalent to prevent sends to imported complaint contacts.
Suppression timestamps and history — The original date a contact unsubscribed, bounced, or complained in your source platform does not transfer to Sender. The suppression event in Sender is recorded with the date you apply the status change.
Soft bounce history — Soft bounces are temporary delivery failures and are not typically migrated as suppression data. Sender handles soft bounces automatically during sending.
How to Test the Migration
Verify unsubscribed status — Go to Subscribers and click the Email status dropdown filter. Select Unsubscribed to view all contacts with that status. Confirm the count matches the number of contacts you imported from your unsubscribe file. Hover over the envelope icon next to a sample contact to verify their status reads "Unsubscribed."
Confirm suppressed contacts are excluded from sends — Create a test email campaign and proceed to the recipient selection step. Select a group that includes both active and suppressed subscribers. Sender should display the count of sendable (active) recipients, which should exclude unsubscribed contacts. Verify the sendable count is lower than the total group count.
Check group assignment — Go to Subscribers → Groups and verify that your suppression groups (e.g., "Imported – Unsubscribes", "Imported – Bounces") show the correct subscriber counts in the Total, Unsubscribed, and Bounced columns.
Spot-check individual contacts — Search for a few specific email addresses from your exported suppression files using the Filter subscribers search bar. Click into each subscriber's profile and confirm the Email campaign section shows the correct status (e.g., UNSUBSCRIBED instead of ACTIVE).
Migration Tips
Import suppression lists before sending any campaigns — Importing and applying suppression statuses must be completed before your first send from Sender. Sending to previously suppressed contacts damages your sender reputation and may violate regulations like GDPR and CAN-SPAM.
Use dedicated groups for each suppression type — Create separate groups such as "Imported – Unsubscribes," "Imported – Hard Bounces," and "Imported – Spam Complaints" to keep suppression data organized and make bulk status changes easier.
Deduplicate across suppression files — If a contact appears in both your unsubscribe and bounce exports, include them in only one file to avoid confusion. Prioritize the most restrictive suppression type.
Keep your original export files — Save the exported .csv files from your source platform as a backup record of suppression data at the time of migration. This provides an audit trail if questions about compliance arise later.
Process suppression lists in batches if the list is large — If your suppression file exceeds 64MB, split it into smaller files. Import and apply statuses to each batch before proceeding to the next to avoid losing track of which contacts have been processed.
Common Issues
Imported contacts show as Active instead of Unsubscribed → Sender's import does not map a status column. Contacts are imported as Active by default. After import, select the contacts via their group and use Actions → Unsubscribe to apply the correct status.
Cannot find a Status field during column mapping → The Select field dropdown during import only includes data fields (E-mail, Phone number, First name, Last name, Birthday, and custom fields). Subscriber status is not a mappable field. Skip the status column during import and apply the status manually afterward.
Suppression group shows 0 Unsubscribed after import → You have imported the contacts but have not yet applied the status change. Go to Subscribers, filter by the suppression group, select all, and click Actions → Unsubscribe.
Bounced contacts still show as Active → The Bounced status cannot be applied through the dashboard. Use Actions → Unsubscribe to prevent sends, or contact Sender support at support@sender.net to apply the Bounced status in bulk.
Duplicate contacts across suppression and active lists → If a contact exists in both your active subscriber import and your suppression import, the status you apply last takes effect. Import and activate your subscribers first, then import and suppress your suppression lists to ensure the suppressed status overrides the active one.
FAQs
Can I import a suppression list with the status column already set? No. Sender's import tool does not include a status field in the column mapping step. All imported contacts are added as Active by default. After importing your suppression list, you must manually apply the Unsubscribed status using Actions → Unsubscribe from the subscriber list.
Do I need to import suppression contacts into a group? It is strongly recommended. Assigning suppression contacts to a dedicated group during import (e.g., "Imported – Unsubscribes") allows you to easily filter and select those contacts later to apply the correct status in bulk.
Will unsubscribed contacts count toward my subscriber plan limit? Unsubscribed contacts remain in your subscriber list but are excluded from campaign sends. Check Sender's current billing documentation to confirm how unsubscribed contacts affect your plan limit.
What happens if I skip migrating my suppression list? Sender will treat those contacts as eligible to receive campaigns. Sending to previously unsubscribed or complained contacts can result in spam complaints, damage to your sender reputation, and potential violations of anti-spam regulations.
Can I use the Sender API to import contacts with a specific status? Sender provides an API that may support setting subscriber statuses programmatically. Go to Account settings → API access tokens to generate a token, and refer to the API documentation by clicking View API docs for available endpoints. This approach may be more efficient for large suppression lists.
How do I handle contacts who unsubscribed from a specific list but not globally? Sender treats unsubscribes as account-wide. If your source platform supported list-level unsubscribes, you will need to determine whether each contact should be globally unsubscribed in Sender or kept as active in certain groups. Import only globally unsubscribed contacts into your suppression group.