Can you use ColdSend inboxes outside of ColdSend?
Short answer: No. ColdSend inboxes work only inside ColdSend.
Why the restriction?
1. Domain authentication is locked to our infrastructure
When you delegate your domain to ColdSend we generate and host the SPF, DKIM and DMARC records on our name-servers.
The private DKIM key never leaves our environment, so no external platform can sign mail on your behalf.
2. Inboxes are logically “registered” to our IPs
Each mailbox is tied to a dedicated ColdSend IP that is pre-warmed and monitored for reputation. Exporting the SMTP
credentials would let you send from a different IP range, instantly breaking the warm-up chain and putting both your
domain and our IP pool at risk.
3. We don’t expose SMTP/IMAP credentials
ColdSend uses a closed API; we do not provide host-names, ports, usernames or passwords that third-party tools
require. Without those details, Instantly, Smartlead, Reply.io, etc. cannot add the inbox in the first place.
No other email platform allows you to do the same, and for the same reason: none of them (Instantly, Smartlead,
Reply.io, etc.) expose SMTP credentials — so the mailboxes stay locked inside the platform where they were created
Bottom line
If you need to split traffic across multiple platforms, register a second sub-domain (e.g. outreach.yourcompany.com) and
delegate that sub-domain to the other service. ColdSend will continue to manage the original domain; the other platform
can manage its own DNS and reputation independently.