If you see "Error creating sequencer," "Error adding accounts," a 422 error, a "Domain unavailable" message, or an account that can't be selected when connecting to a sequencer, here's how to resolve it.
Use the right credentials
In Settings → Sequencers, the Configure step for Instantly and Smartlead uses your sequencer login email + password — not an API key. (Workspace Name, API key, and Consent URL fields are optional.) A common cause of connection errors is entering the wrong login or having 2FA enabled on the sequencer account.
Already connected to another Maildoso account?
A sequencer login can normally be actively connected to only one Maildoso account at a time. If that same Smartlead or Instantly login is still connected to a different Maildoso account, connecting it here can fail with "Error creating sequencer." Disconnect it from the other account first, or contact us to clear the old connection. Full details: "Error creating sequencer" when connecting Smartlead or Instantly.
Instantly: 422 error or "Domain unavailable"
If Instantly itself returns a 422 status or says a domain is "unavailable" when you try to add or reconnect a mailbox, this is almost always the domain or mailbox not being in a fully Active state on Maildoso's side yet, rather than something wrong in Instantly. Instantly's own support will often point back to Maildoso for this message — that's expected, since the check that's failing is on our end.
Before contacting support, check:
The domain and mailbox show as fully Active (not still provisioning) in your Maildoso dashboard. A domain or mailbox created in the last 24 hours may not be ready yet — see provisioning timing.
DNS has fully propagated for that domain (this can lag even after Maildoso shows the domain as connected).
You're reconnecting with current credentials — IMAP/SMTP credentials can go stale if the mailbox was reset or recreated.
If the domain/mailbox is Active and DNS has propagated but you still get a 422 or "Domain unavailable," contact support with the domain name, the mailbox address, and roughly when you first saw the error — this usually needs a backend check on our side.
Google Workspace vs SMTP
Google Workspace mailboxes: connect via Settings → Sequencers, then Email accounts → Add to sequencer.
SMTP mailboxes: export to CSV (use the "Other" format if your tool isn't listed) and bulk-upload in the sequencer. See How do I upload emails to my cold email tool?
If your login is correct and it still fails, it's likely a backend error on our side — contact support and we'll fix it.