Contact validation and quarantine
See how Tantra checks email syntax, role addresses, and MX records before a cold email campaign sends, and why some contacts are quarantined.
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Overview
Before a cold email campaign enrolls its contacts, Tantra runs a validation check on each recipient. Addresses that look risky or undeliverable are set aside in a quarantine so they are not emailed. This protects your sending reputation, since a bad list can hurt deliverability for every mailbox on your domain.
How it works
Validation runs when you launch a cold email campaign, after your suppression and unsubscribe lists have already been applied. Each remaining recipient goes through three checks in order.
- Syntax check. The address must be a single line with one
@and no spaces, and the part after the@must contain a dot. Anything else fails as invalid syntax. - Role-address check. Generic mailboxes that belong to a team rather than a person are flagged. These include local parts such as
info,contact,sales,support,hello,admin,marketing,no-reply,noreply,postmaster,abuse,webmaster,billing,accounts,hr,jobs, andcareers. - MX check. Tantra looks up the recipient domain to confirm it has mail servers. A domain with no mail records fails.
A contact that fails any check is not enrolled. It is placed in quarantine with the reason recorded. Contacts that pass all three checks are enrolled and can receive email.
Quarantine as a state
Quarantine is a state a contact can enter during validation, not a place you file contacts by hand. Quarantined contacts for a campaign appear in that campaign's Needs Review area, each with its email, the failure reason, and when it was quarantined.
The possible reasons are:
- invalid_syntax, the address is malformed.
- role_address, the mailbox is a generic team address.
- no_mx, the domain has no mail servers.
Before you start
- This applies to cold email campaigns. Calendar campaigns do not run this pre-send check.
- Clean your list before launch so fewer contacts are quarantined. See Import contacts from CSV.
What happens next
When you launch a campaign, eligible contacts are enrolled and quarantined contacts are counted separately. Open the campaign and look at the Needs Review area to see which contacts were held back and why. Quarantined contacts stay out of the sequence, so they are never sent to.
The Release for next launch button shown next to each quarantined contact is not yet available. It is labeled as coming soon, so you cannot release a quarantined contact back into sending from this screen today. To try a contact again, correct the underlying address in your contact record and start a fresh campaign.
Best practices
- Send to named people rather than role mailboxes. Role addresses convert poorly and raise complaint rates.
- Fix or drop malformed emails at import time, where the mapping step already flags bad rows.
- Treat a large quarantine as a signal that the source list needs cleaning before you scale up.
Common mistakes
- Assuming every uploaded contact will be emailed. Failing addresses are held in quarantine instead.
- Targeting shared inboxes like
sales@company.com. These are flagged as role addresses.
Troubleshooting
| Symptom | Cause | Fix |
|---|---|---|
| A contact shows reason invalid_syntax | The email is malformed, for example it has a space or no dot after the @ | Correct the address in the contact record, then start a new campaign |
| A contact shows reason role_address | The mailbox is a generic team address | Replace it with a named person's mailbox where possible |
| A contact shows reason no_mx | The domain has no mail servers | Verify the domain is correct, or remove the contact |
| Everything was expected to send but the count is lower | Quarantined and suppressed contacts are excluded before sending | Check the Needs Review area and your suppression list |
FAQ
When does validation run?
It runs when a cold email campaign is launched, after your unsubscribe and suppression lists have already been applied.
Can I release a quarantined contact back into the campaign?
Not from the interface today. The release action is labeled as coming soon and is disabled. Fix the address in the contact record and run a new campaign instead.
Why are role addresses treated as risky?
Team mailboxes such as info@ and support@ often triage marketing as spam, so sending to them lowers deliverability and conversion.
What if a domain check is briefly unreachable?
If the domain lookup times out or hits a transient error rather than a clear no-records answer, the contact is allowed through, and any real problem is caught later at send time as a bounce.
Does this apply to calendar campaigns?
No. This pre-send validation is part of the cold email path only.
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