OpenSRS Hosted Email Spam and Rejections Guide

Hosted Email uses an in-house spam-filtering system designed to block unwanted messages, protect outbound IP reputation, and align with the OpenSRS Email Acceptable Use Policy (AUP). When mail is unexpectedly blocked, bounced, or marked as spam, you can work through the checks below to identify the cause and resolve the issue for your end users.

How Hosted Email spam protection works

The Hosted Email spam solution evaluates inbound and outbound mail against multiple signals: domain authentication records, recipient and sender block lists, mailbox filters, and message content. Per-user training also adjusts how aggressively messages are scored over time. Most delivery failures fall into one of two categories: an SMTP rejection (the message is refused at send time) or a bounce-back (the message is accepted by Hosted Email but rejected by the receiving server).

Initial troubleshooting checklist

Run through the following checks before escalating any spam or rejection issue.

• Verify MX records. Confirm the user's domain has the correct MX records for the cluster it lives on. Cluster A uses mx.domain.tld.cust.a.hostedemail.com and Cluster B uses mx.domain.tld.cust.b.hostedemail.com. See Configure MX records for Hosted Email.
• Check the spam handling mode. Confirm the user is not set to Reject Spam. Passthrough or quarantine modes deliver suspicious messages to the spam folder rather than blocking them outright.
• Review block lists and webmail filters. Check the user's allow and block lists and webmail filters. Confirm the recipient is not blocking the sending IP, IP range, domain, or sender. The sending IP appears at the end of the Received-SPF header line.
• Check sender authentication. Validate that the sender's SPF, DKIM, and DMARC records align with the message headers. Look for the DKIM result on the X-HE-DKIM-Result line. If SPF or DKIM fails, the sending domain's DMARC policy can explain why the message was rejected or scored as spam.

When customers cannot send email

To diagnose outbound send failures, distinguish between an SMTP rejection and a bounce-back rejection.

An SMTP rejection happens when the user's mail client or webmail returns an error at send time. Hosted Email is refusing the message before it leaves the platform.

A bounce-back rejection arrives after the user sends the message. The bounce message lands in the sender's inbox and explains that the receiving server rejected the message after delivery was attempted.

SMTP rejection troubleshooting

• Validate the user account. Confirm the user is not disabled or suspended, that SMTP and Webmail Send are enabled, and that the user has not exceeded the daily outbound mail ceiling. See User status and sending capabilities.
• Review the message itself. Ask the user to save a draft of the message and inspect it. Large recipient lists or content patterns can trigger spam scoring on outbound mail. Confirm the message meets the OpenSRS Email AUP.

Bounce-back rejection troubleshooting

Ask the user for the full text of the bounce message. The receiving server usually states why the message was rejected. Common reasons include:

• The recipient address does not exist.
• The recipient's mailbox is full.
• The sender failed SPF, DKIM, or DMARC policy checks.
• The sending IP is on an external blocklist. For blocklist scenarios, escalate to OpenSRS Support — depending on the list, the team may be able to request delisting.

Email client rejection errors

Outbound spam scoring has resulted in some mail clients (notably Outlook) returning errors such as "recipients do not exist" at send time. This error is generated by the client itself, not by Hosted Email, and usually reflects a misconfiguration in the client.

Review the client's account settings and outbound configuration. OpenSRS Support cannot override this error and does not troubleshoot third-party email applications.

Mark an email as spam

Marking a message as spam trains the filter using the sender, headers, and content of the message. The filter then weights similar future messages more aggressively. Marking a message as not spam trains the filter to treat similar messages as safe.

1. In webmail, select the message and choose Spam.
2. Press Accept to confirm the message as spam.

When to escalate to support

If you have worked through the checks above and still cannot determine why a message was rejected or delivered to spam, contact OpenSRS Support. To speed up investigation, include:

• Your reseller ID (the account name used at signup)
• Your authorized user ID (the login used at manage.opensrs.com)
• The recipient's email address
• The sender's email address
• The date, timestamp, and timezone of the failure

Next steps

• Review the spam-scanning solution overview. Understand how scoring and per-user training affect filter behavior. See Hosted Email Spam-Scanning Solution.
• Tune missed spam handling. If users continue to see spam in the inbox, adjust the spam threshold and report examples to support. See Managing Missed Spam Messages.
• Configure allow and block lists. Approve trusted senders and block known bad ones at the user, domain, or company level. See Set Allowed and Blocked Sender Lists.

Questions? Contact OpenSRS Support.