Constant Contact merge lists: combine your spreadsheets into one clean file first

Merging two lists in Constant Contact? Lists already in your account merge natively with Actions > Merge, and each contact appears once. Lists in outside spreadsheets have to be combined and imported, and the same person with a second email address becomes a second contact. Below: Constant Contact's own steps first, then our done-for-you cleanup of your combined file: same-email duplicates merged, possible duplicates flagged and a change log, back in 24 hours on Quick Clean (up to 200 rows).

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How to merge lists in Constant Contact: what you can do natively

If the lists are already in your account, Constant Contact merges them for you: "When you merge multiple contact lists together, you can choose to move all contacts from your selected lists into a new or existing list." Each person shows once: "If a contact is on multiple lists being merged, the contact appears only once in your resulting list." (Constant Contact Knowledge Base: Merge multiple contact lists into a single list) If some of your lists are outside spreadsheets, combine those files first and import one file. Here is how to merge two lists in Constant Contact, or combine lists from outside it.

Export what's already in your account. Select the contacts, then "Click Actions > Export selection." "Did you know? Instead of choosing individual contacts, you can also export contacts that are part of a specific list or segment, or that are assigned a particular tag." If you track CASL or GDPR permission: "The exported spreadsheet doesn't include the permission status unless the permissions are enabled." (Constant Contact Knowledge Base: Export your email or SMS contacts into a spreadsheet)
Lists already in the account: Route A, Actions > Merge. "From the Lists and Segments page, click the Lists option next to the Search field." "Select the combination of lists you want to merge." "Click Actions > Merge." Name the new list: "List names are limited to 255 characters and must be unique." Then "Click the Add button." The old lists stay: "After your lists are merged, the original lists remain as-is, and you can always rename or delete them later." Other lists aren't touched: "If the same contact is on other lists that weren't merged, they remain on those lists." (Constant Contact Knowledge Base: Merge multiple contact lists into a single list)
Lists outside the account: Route B, combine the spreadsheets. To combine multiple lists into one in Excel, put everything in one sheet: "Use a compatible file type and organize the content so that there aren't multiple tabs." (Constant Contact Knowledge Base: Import a file of email or SMS contacts) Also: "Multiple worksheets - Consolidate all data into the first tab or worksheet and delete extra worksheets." and "Unique column headings - Give every column a unique label." (Constant Contact Knowledge Base: Format a file before importing a contact list into Constant Contact) Then dedupe it, which Constant Contact leaves to you: "Sort your spreadsheet by email address or SMS number to make sure there aren't any duplicates." (Constant Contact Knowledge Base: Common questions and issues when importing contacts from a file)
Import the combined file into one list. "(Optional) Choose the list you want to add your contacts to, or create a new list. You can create and select multiple lists to suit your needs." "Confirm that you have consent to email these contacts." Columns you don't want: "Select Skip field from the drop-down menu if you don't want to import a column of data from your spreadsheet." Existing contacts are updated by email: "If an email address for a contact in your spreadsheet matches a contact's email address that already exists in your Constant Contact account, the contact is updated to prevent duplicate contacts." (Constant Contact Knowledge Base: Import a file of email or SMS contacts) On an existing list: "An existing list - The existing contact is updated, and new contacts are added to the list." (Constant Contact Knowledge Base: Common questions and issues when importing contacts from a file)

Where our cleanup fits: in step 3. Stack your spreadsheets (and any exports from step 1) into one CSV, send it, and import the cleaned file in step 4. Removing duplicates from one account instead.

Before you merge lists in Constant Contact

The in-account merge is permanent: "Once you merge contact lists together, it can't be undone." (Constant Contact Knowledge Base) The original lists stay until you delete them, so keep them until you've checked the new list.
A new email address means a new contact: "If you have a contact in your account who’s also on your spreadsheet with a new email address, a new contact record is created for that contact. This creates two contacts." (Constant Contact Knowledge Base) Constant Contact's advice: "In this case, it’s a good idea to check with the contact to make sure which email address they want to use going forward, so you can remove the duplicate contact record." (Constant Contact Knowledge Base)
Deleting the extra record loses its history: "Important: When you delete a contact record, all of the email engagement information found in the contact record is deleted with it." (Constant Contact Knowledge Base)
Tags must exist first: "Existing tags - Create any tags in your Constant Contact account before importing. Tags included in a spreadsheet that do not already exist in the account will be ignored during import." (Constant Contact Knowledge Base)
Consent is on you: "Confirm that you have consent to email these contacts." (Constant Contact Knowledge Base)

We don't overwrite your values. Our cleanup keeps every column in your files, including email status and permission columns. When two rows share an email, a blank cell on the kept row can be filled from the other row; every fill is listed in the change log. When both rows disagree in a consent-type column we recognise by header name (for example a column with "permission", "status" or "unsubscribed" in its header), the row is flagged needs_review with both values in qa_notes, and the first row's value is kept. So if someone is subscribed on one list and unsubscribed on another, you see it before you import. You run the merge and the import in Constant Contact. We never log in to or touch your Constant Contact account.

Or let us clean the combined file before you import

You stack your spreadsheets and exports into one CSV or Excel (.xlsx) file (same columns, one header row) and send it. With Excel, we clean the first sheet of the workbook, and the file comes back as a cleaned CSV plus a change log. We don't take old Excel .xls files; save them as .xlsx or CSV first. We clean one file per job and don't add a column showing where each row came from, so before stacking, add one column yourself: "Source list" (the list or spreadsheet each row came from). If your file has a plain Email or Email Address column, that's the email we use, wherever it sits. Other columns with "email" in the header (opt-in, status or permission columns, or ones you add) are kept as their own columns, and one only fills a blank email when it holds a real address. If you add your own Status column, it comes back as status_src, because the cleaned file has its own status column. Pricing is by rows in the stacked file you send. We never log in to Constant Contact. We don't merge lists, delete contacts or run the import.
Rows with the same email (ignoring capitalization and spaces at the start or end) are merged into one row, so a person who was on two lists appears once: the first row is kept and its blank fields are filled from the later rows, which can include consent cells. Where both rows have different values, the first row's value is kept and the other is listed in the change log. List values aren't combined: if the two rows have different "Source list" values, the first is kept and the other is listed in the change log. Stack your main list first if you want its values kept. Every merge and every fill is listed in the change log.
Rows with the same full name and the same company, where both are present, but a different or missing email are flagged, not merged. That is the "new email address" case above, when your files have a company column. Each one is marked needs_review, with a note naming the row it may match. Constant Contact asks you to check these yourself ("Review the highlighted content to ensure they are truly duplicate contacts and not simply contacts with similar names.", Constant Contact Knowledge Base), and the flag list is where you start. Rows with no company aren't compared, so a person with two emails and no company isn't flagged.
Invalid, missing and personal (for example Gmail or Yahoo) emails are flagged in qa_notes. We don't fix or verify mailboxes.
Names in ALL CAPS or all lowercase are re-cased. Constant Contact doesn't do this on import: "Text Casing - Text is imported exactly as formatted in your file. Names starting with lowercase letters will remain lowercase and will not auto-capitalize upon import." (Constant Contact Knowledge Base) US phone numbers are formatted +1-XXX-XXX-XXXX. Numbers with a non-US country code (starting with + or 00) are kept as you sent them (extra spaces trimmed only). Numbers with no country code and 10 digits are treated as US. Placeholder phones like N/A are blanked and logged; Constant Contact asks for this for SMS: "SMS formatting - Ensure phone numbers and consent dates do not contain placeholder values such as "N/A" or all zeros." (Constant Contact Knowledge Base) Anything we can't read is kept as-is, with a note in qa_notes. Line breaks inside cells are turned into spaces (except in the email column, where a broken email is flagged invalid instead), and the CSV is saved as UTF-8. Rows with no company get a "missing company" note and are marked needs_review. Filter qa_notes for "merged duplicate", "possible duplicate" and "consent conflict" to find the rows that matter.
You get back the cleaned CSV (with status, qa_notes and source_row columns), a change log with every merge, every fill from a duplicate, every email and possible-duplicate flag, and every edited cell listed by row, with its old and new value, a QA report with counts (rows in and out, duplicates merged, possible duplicates flagged, emails flagged and cells edited), and your original file, unchanged. Choose "Skip field" for status, qa_notes and source_row when you import.
What we don't do: we don't merge lists, delete contacts or edit anything inside Constant Contact. We don't run the import, map fields, choose lists or create tags, and we don't combine list or tag values from two rows into one. We don't promise deliverability, inbox placement or bounce rates, or a lower Constant Contact bill, we don't verify mailboxes, we don't find, buy or add contacts, and we don't merge rows that only might be the same person.

Clean my combined Constant Contact lists · $25 (up to 200 rows, back in 24h)

Rather hand off the cleanup? $25 Quick Clean: up to 200 rows, cleaned CSV (same-email duplicates merged, possible duplicates flagged) plus a change log within 24 hours.

Bigger list? Intro $99 for up to 500 rows (48h) · Growth $299 for 501 to 2,000 rows (72h) · Bulk $499 for 2,001 to 5,000 rows (5 business days) · over 5,000 rows, custom quote. See all sizes.

What you get back

Every change is logged with its original row number.
Possible duplicates are flagged for your review, never blind-merged; same-email duplicates are merged and listed in the change log.
Your original file is returned alongside the cleaned one.

See a free before-and-after sample · sample files you can download

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How it works

Pay

Pick the size that fits your list and check out on Stripe. Quick Clean is $25 for up to 200 rows.

Email us your CSV (reply to your receipt or send it to slrescue@mail.grokbot.com)

No Constant Contact login, no call, no upload form.

Get it back: 24h (Quick Clean, up to 200 rows), 48h (Intro), 72h (Growth), 5 business days (Bulk)

A clean CSV plus a change log. Over 5,000 rows, the turnaround is scoped in your custom quote.

Flat pricing

Quick Clean, up to 200 rows, back within 24h, $25 (credits toward a larger pack within 14 days)
Intro, up to 500 rows, back within 48h, $99
Growth, 501 to 2,000 rows, back within 72h, $299
Bulk, 2,001 to 5,000 rows, 5 business days, $499
Over 5,000 rows: email us for a custom quote

Your $25 Quick Clean counts toward any bigger cleanup within 14 days.

Quick Clean, Intro, Growth and Bulk: If the file isn't what we promised, we fix it once for free within 48 hours. If it still isn't right, you get your money back for the part we couldn't deliver. If we're late, you choose a full refund or a free rush job.

Not sure how messy it is? CRM Hygiene Scorecard (written diagnosis), $29. Agencies: white-label batches.

Questions

Can you merge lists in Constant Contact?

Yes, for lists already in your account: "Click Actions > Merge." "If a contact is on multiple lists being merged, the contact appears only once in your resulting list." (Constant Contact Knowledge Base) For outside spreadsheets, combine them into one file and import it (steps 3 and 4). That is the part we clean.

Does a merged list cost more?

Constant Contact's import guide says: "You're only charged for unique contacts in the "Active" status, which means you can add a single contact to multiple lists, and email them as often as you need to without affecting your bill." (Constant Contact Knowledge Base) The same person with a second email address is a second contact (see the caution box). We flag those pairs when name and company match; we don't promise a lower bill.

Should I use lists, tags or segments?

Constant Contact: "It's fine if a single contact appears on more than one list! When you send an email, you can choose which lists receive it, and if you have any duplicate contacts on multiple lists, we'll only send them one email." (Constant Contact Knowledge Base) Segments can't be merged: "Segments aren't compatible with lists and can't be merged." (Constant Contact Knowledge Base)

What happens to someone subscribed on one list and unsubscribed on another?

In our cleanup, when both rows share an email and the values differ in a permission or status column, the row is flagged needs_review with both values listed, and the first value is kept. You decide before you import.

Will you merge or delete anything in my Constant Contact account?

No. We clean the stacked file only. Same-email rows are merged in the file, with each merge and fill logged. You run the list merge, any deletes and the import in Constant Contact yourself.

What comes back, and how do I import it?

A UTF-8 CSV, also when you send Excel (.xlsx), plus a change log. Headers come back in lowercase with underscores (for example, Source list becomes source_list and Email permission status becomes email_permission_status), and the email column comes back as email. Our standard columns come first (full_name, then first_name and last_name when your export has them, then email, phone, company, title, website and linkedin; some may be blank), then status and qa_notes, then the rest of your columns and source_row. Skip status, qa_notes and source_row: "Select Skip field from the drop-down menu if you don't want to import a column of data from your spreadsheet." (Constant Contact Knowledge Base) We don't run or guarantee the import.

Do you need access to my Constant Contact account?

No. You export a file and email it. We only clean the exported file and never log in to or touch your Constant Contact account.

How fast is delivery?

From when we receive your file: Quick Clean (up to 200 rows) within 24 hours, Intro within 48 hours, Growth within 72 hours, Bulk within 5 business days. Over 5,000 rows is scoped in your quote.

What if the cleaned file isn't right?

If the file isn't what we promised, we fix it once for free within 48 hours. If it still isn't right, you get your money back for the part we couldn't deliver. If we're late, you choose a full refund or a free rush job.

What happens to my data?

Your file is used only for your job and deleted after delivery on request (see Anonymous aggregate statistics). We never log in to your CRM, and we never invent, buy, or append emails.

Anonymous aggregate statistics. After a cleanup we keep a small record of counts about your file: rows in and out, duplicates merged, rows flagged for review, which fields were present, and the CRM you told us it's for. This record contains no contact data, names, emails, company names, domains, file names or cell values, and it isn't deleted when your file is deleted. We only publish these counts combined with at least 19 other lists (and at least 5 different customers), so no single customer can be identified. To opt out, reply 'opt out' to your delivery email and we'll delete your record.

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Not affiliated with Constant Contact. Quotes are from Constant Contact's public help docs.