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Testing Mail Flow

Alex Panagides
Updated

After you set up routing, test it with a few test users before you route everyone. This page gives a test plan, what to look for in message headers and in Reports › Email Flow Logs, and how to read the most common results.

Before you begin

  • Routing is configured for your platform, with the routing rules limited to a pilot group or still turned off. See Selective routing.
  • Each domain has its Server set in Settings › Organization and domains.
  • You have one or two test mailboxes in your domain and a mailbox outside your organization (for example a personal account).

Step 1: Create a test rule

Use a rule that is easy to see and harmless to recipients.

  1. In the Admin Dashboard, open Rules › Create a Rule.
  2. Choose Copy Emails. It saves a copy to storage and delivers the original unchanged.
  3. Target Email Flow, with the test user as sender or recipient.
  4. Choose a test folder in your storage and save the rule.

See Create a rule. New and changed rules take about 1–2 minutes to apply.

Step 2: Turn on routing for the test users

  • Microsoft 365: turn on mxHERO - Route Inbound and/or mxHERO - Route Outbound, limited to the pilot group. Allow up to an hour for Exchange Online to apply rule changes.
  • Google Workspace: save the content compliance rules with the pilot group envelope filter. Allow up to an hour.
  • Border or MX: change the gateway or the MX record.

Step 3: Send test messages

Test From To Expected result
Inbound Outside mailbox Test user Delivered once; a copy is in the test folder
Outbound Test user Outside mailbox Delivered once; a copy is in the test folder
Internal Test user Another user in your domain Delivered once
Not in pilot Outside mailbox User not in the pilot group Delivered; not in Email Flow Logs
Attachment Outside mailbox Test user, with an attachment Delivered; attachment copied

Step 4: Check the message headers

Open the message the test user received and view its full headers:

  • Outlook on the web: open the message › More actions (…) › View › View message details.
  • Gmail: open the message › More (⋮) › Show original.
Header What it tells you
X-mxHero-Server: <value> The message went through mxHERO and mxHERO recognized your Transport Agent value. The value equals Settings › Gateway.
No X-mxHero-Server The message did not go through mxHERO, or it went through without a valid Transport Agent value.
X-mxHero-Transport-Agent Should not be present on delivered mail; mxHERO removes it.
ARC-Seal with d=mxhero.com mxHERO sealed the message.
Authentication-Results with compauth=pass reason=130 (Microsoft 365) Microsoft 365 trusted the mxHERO ARC seal.
Many Received headers through mxHERO and your mail system A loop. See Troubleshooting.

Step 5: Check Email Flow Logs

  1. Open Reports › Email Flow Logs.
  2. Search by Sender, Recipient or Subject, with a date range that includes your test.
  3. Open the message. Check:
    • the email actions: Mail Received, Mail Split, Rule Executed for your rule, and Mail Delivered ;
    • the recipient's latest status and, in the recipient details, the relay, delay and SMTP status of the final delivery.

See Email Flow Logs. New entries can take up to a minute to appear.

What you see Meaning
Message present, rule executed, delivered Routing and the rule work.
Message present, rule not executed, with a reason (for example flow_filter_from_to, mail_content_without_attachments) Routing works; the rule didn't match. Adjust the rule.
Rule Execution Failed The rule failed; the original was delivered unchanged. Check the error and Reports › Notifications.
Message not present The message didn't reach mxHERO, or Only process email rules with transport agent header (Strict Mode) is on and the Transport Agent value was missing or wrong.

Step 6: Roll out

When all tests pass:

  1. Expand the routing rules to everyone, or add users to the pilot group. See Selective routing.
  2. Disable or delete the test rule.
  3. Create your production rules, and tell users what to expect. See Planning end user communications.

Troubleshooting

Symptom Cause Fix
Duplicate messages, or bounces with 554 Message exceeded 50 hops, this may indicate an email loop. Loop exception wrong (tests X-mxHero-Transport-Agent instead of X-mxHero-Server, wrong value, wrong match type), host uses MX lookup, or Server missing Turn routing off, fix the exception and Server, test again. See Mail loops and bounces.
Message delivered but not in Email Flow Logs Routing rule not active yet, user not in the pilot group, or Strict Mode on with a missing or mismatched header Wait for rule changes to apply. Check group membership. Copy the value again from Settings › Gateway.
In Email Flow Logs but the rule didn't run Rule conditions don't match, or the rule was saved less than 2 minutes ago Read the reason in the event list. See How rules work.
Test user's mail goes to spam Mail system doesn't trust mxHERO IP addresses Check the connection filter (Microsoft 365) or inbound gateway (Google).
Outbound mail rejected by the recipient's server for SPF include:_spf.mxhero.com missing Update SPF. See SPF, DKIM and DMARC.

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