How to Block Leads from Forwarding Email Domains in Your System

Charlie B. · 2025-12-19T11:02:19.627Z

Hello! I have a block list of domains that are existing customers. How do I make sure that leads with email address domains that forward to those blocked domains dont get through? I've run an initial check to block the known domains. But email addresses that forward to those domains aren't being blocked

How to Block Leads from Forwarding Email Domains in Your System | Clay

14 comments

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Clay Support
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Email forwarding breaks standard domain blocking because the forwarding server's IP isn't in your original domain records—this is a fundamental limitation. [1]
For Clay workflows, you can:
• Use conditional formulas to check if domains contain forwarding patterns [2]
• Set up comparison operators with "contains" logic to catch common forwarding domains [3]
• Add domains to your EmailBison blocklist using the "Add domain to blocklist" action [4]
The most reliable approach is expanding your blocklist to include known forwarding domains and using conditional logic to flag suspicious patterns before they reach your campaigns.
Clay Support
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Is that what you were looking for?
Charlie B.
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Makes sense, so just find all possible forwarding domains? How would I form the conditional formula to check patterns?
Clay Support
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For conditional formulas to check forwarding patterns, use the "contains" operator with OR logic: [1]
IF (email contains "@gmail.com" OR email contains "@yahoo.com" OR email contains "@outlook.com") return "Block - Personal/Forwarding Domain" ELSE return "Allow"
You can also check multiple patterns in one condition: [2]
IF (email.domain contains any of ["gmail", "yahoo", "hotmail", "protonmail"]) return "Block" ELSE return "Allow"
Use logical operators (&&, ||) to combine conditions—like checking both domain patterns AND other criteria. [3] Build this in an AI Formula column to flag suspicious emails before they hit your campaigns. [4]
Clay Support
APP
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Did that answer your question?
Clay Support
APP
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If you need any more help with setting up your conditional formulas or managing your blocklist, I’m here to assist. Would you like to provide more details about what you’re trying to achieve or any specific challenges you’re facing?
Charlie B.
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No it didn't
Clay Support
APP
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I understand this can be frustrating. I’m connecting you to a human agent who can assist you further.
Clay Support
APP
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Our support team has got your message and we'll get back to you soon! We're currently outside of our standard office hours (9 AM to 9 PM EST, Monday through Friday), so it may take a little longer for us to respond.

If you’re dealing with a specific table, drop the URL below so we can help you quicker. Otherwise, someone from our team will be in touch soon!

image.png(93 kB)
Charlie B.
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The blocked one it - https://www.costcuttersuk.com/ The one that is forwarding to the blocked is - seatedfurnitureonline.com
Charlie B.
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I know the format is off. Seated furniture itself isn't blocked. But cost cutters is but seated furniture forwards to cost cutters
Charlie B.
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I hope that makes sense.
Michael A.
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Hi Charlie - thanks for reaching out!
Can you send me the table URL you'd like help in? Unfortunately, there's no straightforward way to detect where an email address forwards to because that information is private and not exposed through standard email validation or DNS records.
If an email's MX records point directly to your blocked customer's mail servers, you might be able to catch those using Google's MX?
Clay Support
APP
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We haven't heard back from you here, so we're going to go ahead and close this thread out.

Still need help here? Reply back and someone will jump back in.

Have a question thats not related to this thread? We recommend kicking off a new ticket in the support channel!

Clay Support
APP
·
·
Email forwarding breaks standard domain blocking because the forwarding server's IP isn't in your original domain records—this is a fundamental limitation. [1]
For Clay workflows, you can:
• Use conditional formulas to check if domains contain forwarding patterns [2]
• Set up comparison operators with "contains" logic to catch common forwarding domains [3]
• Add domains to your EmailBison blocklist using the "Add domain to blocklist" action [4]
The most reliable approach is expanding your blocklist to include known forwarding domains and using conditional logic to flag suspicious patterns before they reach your campaigns.
Clay Support
APP
·
·
Is that what you were looking for?
Charlie B.
·
·
Makes sense, so just find all possible forwarding domains? How would I form the conditional formula to check patterns?
Clay Support
APP
·
·
For conditional formulas to check forwarding patterns, use the "contains" operator with OR logic: [1]
IF (email contains "@gmail.com" OR email contains "@yahoo.com" OR email contains "@outlook.com") return "Block - Personal/Forwarding Domain" ELSE return "Allow"
You can also check multiple patterns in one condition: [2]
IF (email.domain contains any of ["gmail", "yahoo", "hotmail", "protonmail"]) return "Block" ELSE return "Allow"
Use logical operators (&&, ||) to combine conditions—like checking both domain patterns AND other criteria. [3] Build this in an AI Formula column to flag suspicious emails before they hit your campaigns. [4]
Clay Support
APP
·
·
Did that answer your question?
Clay Support
APP
·
·
If you need any more help with setting up your conditional formulas or managing your blocklist, I’m here to assist. Would you like to provide more details about what you’re trying to achieve or any specific challenges you’re facing?
Charlie B.
·
·
No it didn't
Clay Support
APP
·
·
I understand this can be frustrating. I’m connecting you to a human agent who can assist you further.
Clay Support
APP
·
·
Our support team has got your message and we'll get back to you soon! We're currently outside of our standard office hours (9 AM to 9 PM EST, Monday through Friday), so it may take a little longer for us to respond.

If you’re dealing with a specific table, drop the URL below so we can help you quicker. Otherwise, someone from our team will be in touch soon!

image.png(93 kB)
Charlie B.
·
·
The blocked one it - https://www.costcuttersuk.com/ The one that is forwarding to the blocked is - seatedfurnitureonline.com
Charlie B.
·
·
I know the format is off. Seated furniture itself isn't blocked. But cost cutters is but seated furniture forwards to cost cutters
Charlie B.
·
·
I hope that makes sense.
Michael A.
·
·
Hi Charlie - thanks for reaching out!
Can you send me the table URL you'd like help in? Unfortunately, there's no straightforward way to detect where an email address forwards to because that information is private and not exposed through standard email validation or DNS records.
If an email's MX records point directly to your blocked customer's mail servers, you might be able to catch those using Google's MX?
Clay Support
APP
·
·
We haven't heard back from you here, so we're going to go ahead and close this thread out.

Still need help here? Reply back and someone will jump back in.

Have a question thats not related to this thread? We recommend kicking off a new ticket in the support channel!