Know when email slows down before your users do

Mailflow Monitoring sends test messages through your mail system around the clock, measures every leg of the round trip every 5 minutes, and alerts you the moment delivery slows or fails.

Round-trip SMTPInbound & outboundEvery 5 minutesReal-time alertsGoogle Workspace & Microsoft 365

Included in Delivery Center, with expert email delivery insight on top.

Get Mailflow Monitoring $129/mo Free Email Server Test

Delivery Center is $129/month and comes with a 30-day money-back guarantee. Compare all plans →

Email slow right now?

Run these free checks first:

Email server (SMTP) test: response time and errors
Blacklist check: listings that delay or block mail
MX lookup: where your inbound mail is going

Then set up Mailflow Monitoring so you hear about the next one first.

Part of Delivery Center

Mailflow Monitoring is included in every Delivery Center plan, from $129/month, alongside DMARC, blacklist monitoring and Inbox Placement.

Compare plans →

What we measure

Metric	What it tells you
Round-trip delivery time	How long a message takes to leave your system and come back, end to end
Inbound processing time	How quickly your servers accept and process incoming mail
Outbound queue delay	Whether mail is sitting in your outbound queue before it's sent
Server response times	How fast your mail servers answer SMTP connections
Header analysis	Where in the path a delay happened, from inbound and outbound test messages
History and trends	Hourly, daily, weekly and monthly charts with drill-down, recorded every 5 minutes

How it works

Create a mailbox

Set up a mailbox on your mail system that forwards incoming messages to MxToolbox.

Tell us the address

Add the address to your monitor. We handle the rest: sending, receiving and timing every test.

Get alerted

Tests run 24x7. When a round trip slows past your timeout or fails, you're alerted right away.

Get Mailflow Monitoring $129/mo Compare all plans →

Configured for your environment

Monitor each server in a cluster

Point a monitor at a single IP to test individual nodes, so one slow server can't hide behind a healthy cluster.

Your timeouts, your frequency

Set the timeouts that matter for your business and change how often tests run.

Real-time alerts

Configurable alerts tell you as soon as delivery slows or stops, before users start filing tickets.

Cloud email included

Round-trip monitoring works with Google Workspace and Microsoft 365, not just on-premises servers.

Built for the way your team sends

Email Marketers

Know right away when password resets, receipts and other time-sensitive mail are delayed, not after customers complain.

DMARC Adopters

Authentication tells you whether mail is trusted. Mailflow tells you whether it's moving. See both in Delivery Center.

IT Email Administrators

Track queue delays and server response times per node, prove SLAs with history, and get alerted before the help desk does.

20+ years in email deliverability

42K+Domains trust MxToolbox

100+Blacklists checked

500+DMARC-reporting inbox providers

MillionsMessages processed hourly

Part of Delivery Center

Mailflow Monitoring is one piece of a full email reputation toolkit. Paid Delivery Center plans also include:

Adaptive Blacklist Monitoring

Every sending IP, including ESPs, watched on 100+ blacklists.

Learn more →

Inbox Placement

See whether campaigns reach the inbox or spam at Google, Yahoo! and Outlook.com.

Learn more →

DMARC Enforcement

Get compliant, then enforce to protect your brand, sending reputation and business from BEC.

Learn more →

See everything in Delivery Center →

Frequently asked questions

What is round-trip monitoring?

We send a test message to a mailbox on your system, it forwards back to us, and we time each leg. If the round trip slows or fails, something in your mail flow needs attention.

How often are tests run?

Statistics are recorded every 5 minutes, 24x7. You can change the monitor frequency to fit your needs.

Does it work with Microsoft 365 and Google Workspace?

Yes. Round-trip monitoring supports both, as well as on-premises mail servers.

Can I monitor inbound and outbound separately?

Yes. Inbound and outbound tests with header analysis show which direction is slow and where.

Questions? Call 866-MXTOOLBOX (+1 866-698-6652) or contact us →

Catch mail delays before your users do

End-to-end Mailflow Monitoring with expert email delivery insight, included in Delivery Center.

Get Mailflow Monitoring $129/mo

Delivery Center is $129/month, backed by a 30-day money-back guarantee. Compare all plans. Questions? Call us at +1 (866) 698-6652.