How to Match Email Subdomains to One Company Domain

To match emails on subdomains to one company, upload the list to the email subdomain to root domain tool, and use the root_domain column it adds. An address at mail.eu.acme.com then counts as acme.com.

Why it matters

Some companies give staff addresses on a subdomain. A list may hold jane@acme.com, raj@mail.acme.com and li@eu.acme.com. Grouped by the text after the @, that is three companies. Grouped by root domain it is one, so:

• A cap of one contact per company really means one.
• A customer's domain, when you suppress it, catches the subdomain addresses too.
• A count of how many people you hold at each company is right.

What you need

• A CSV or .xlsx lead list with an email column.

Step 1: split out personal mail

Gmail, Outlook.com and Yahoo addresses are not companies, so two people on gmail.com are not colleagues. The free vs business email filter splits them out. Run the root domain step on the company file.

Step 2: add the root domain

Upload the file or paste the cells with the header row first. Each address gets a root_domain column. A subdomain_removed column shows what was cut off, such as mail.eu.

Step 3: check the endings

Normally the last two parts of the name are kept. For endings that have two parts, such as co.uk or com.au, three are kept, so uk.initech.co.uk becomes initech.co.uk. The built-in list covers the common ones and is not the full public suffix list. Skim the counts table for a name that looks cut too far.

Step 4: use the column

Download the list with the new column. Then:

• Cap contacts per company with limit contacts per company, using root_domain as the company.
• Suppress customers with remove emails by domain, using their root domains.
• Count addresses per company with the email domain frequency counter.

Step 5: check the addresses

Matching companies tells you who works where, not whether their mailboxes exist. Upload the list to check the addresses before the send. The pricing page has the plans for bigger lists, and clean list before campaign checklist shows where this step sits in a full routine.

Limits to know

• A company with unrelated domains, such as a parent and a brand, is not joined. Only subdomains of one name are.
• The tool does not check that a domain has a website or a mail server.
• A rare ending outside the built-in list may be cut one part too far.

Frequently asked questions

Is the original email changed? No. The email column is untouched.

What if a row has no readable domain? Its root_domain cell is blank, and the number of such rows is shown above the table.