Emails sent through Zoho Campaigns sometimes end up in a recipient's spam folder, and this is not always caused by the campaign platform itself. In a number of cases we have investigated, the fault sits almost entirely on the recipient's side, specifically in how their domain handles inbound mail forwarding, rather than in the sender's original configuration.
Why Sender Authentication Can Still Pass
When Zoho Campaigns sends an email on behalf of a sending domain, the primary authentication checks are carried out at that point, and in these cases all three passed correctly:
- DKIM signing verified against the sending domain
- SPF check passed for the sending domain
- DMARC policy set to p=REJECT and passed at the point of sending
In other words, the sender's domain setup was working exactly as intended. The problem only appeared further along the delivery chain, after the message left the sender's control.
How the Recipient's Forwarding Chain Breaks Trust
In the case investigated, the recipient had set up an internal forwarding arrangement that unintentionally undermined the message's authentication once it arrived. The chain looked like this (domain names below are illustrative examples):
- Auto-forward set up. The recipient had configured an automatic forward from an address such as test@recipient-uk.com to a group alias such as group-alias@recipient-com.com.
- Forward routed through third-party servers. That forward passed through intermediary mail-handling servers before reaching its destination.
- Message rewritten at the destination. The destination mail platform took the forwarded message, modified its headers and display name, re-wrapped it, and delivered it to the final inbox, for example user@recipient-com.com.
Note: By the time the message reached the final inbox, it had been altered and re-routed across multiple mail networks. This is what triggered the recipient's spam filter, which flagged the message as having been rewritten mid-transit and recorded an authentication alignment failure. We are treating the failure noted in the original investigation as a DMARC alignment failure, but this should be verified against the source ticket, as the original notation was unclear.
What the Recipient Needs to Change
Because the fault lies in the recipient's own inbound routing, it is the recipient's IT team, not the Zoho Campaigns sender, who needs to make a change. There are two options:
- Best practice: remove the auto-forward. Send emails directly to the destination mailbox rather than routing them through an external or web-based auto-forwarder.
- Alternative: whitelist the forwarding path. If the forward cannot be removed, the recipient's IT team should add an explicit allow or trust rule for messages routed through their internal group alias.
If you are troubleshooting a similar spam complaint, it is worth checking the recipient's own forwarding rules before assuming the fault lies with the sending platform. Authentication passing at the point of sending, followed by a failure further down the chain, is a strong indicator that the issue sits on the recipient's side.
Need help? If you are seeing Zoho Campaigns emails land in spam and are not sure whether the cause is on your side or the recipient's, our Zoho AI Consultancy team can help diagnose the delivery chain.
Book a discovery call with 1 Cloud Consultants.