--- title: Email Round-Trip Monitoring for Delivery & Spam description: Email round-trip monitoring by WatchFor. Send a test message through your SMTP server, find it in the mailbox, and alert on delivery time, spam placement, SPF/DKIM/DMARC results and every hop. canonical: https://watchfor.io/email-round-trip-monitoring --- New # Email Round-Trip Monitoring: Prove Your Mail Actually Arrives Your mail server can pass every check and still lose the password-reset email. WatchFor sends a real test message through it, finds it in the mailbox, and tells you how long it took and where it landed. [Start testing delivery](/auth/sign-up)[See plans](/pricing) [Round-trip documentation](/docs/monitors/email-round-trip)[Free email header analyzer](/email-header-analyzer) ## What a Round-Trip Check Measures One message, from your SMTP server to the mailbox, read the way the receiving server wrote it ### Delivery, End to End Each check logs in to your SMTP server on 587 or 465, sends one message, then looks for it in the mailbox over IMAP or POP3 every 2 seconds. Delivery time runs from the moment your server accepted it to the moment it showed up. ### Inbox or Spam Over IMAP the check looks in the Inbox and then in the Junk or Spam folder. Landed in Spam is on by default as a warning: the mail arrived, just not where people will see it. ### SPF, DKIM and DMARC as Received The verdicts come from the receiving server's Authentication-Results header, not from your DNS records, so you see what the real receiver decided about this message. Alerts for each are one click away. ### Spam Score and Antivirus When the receiving filter leaves its score in the headers (SpamAssassin, rspamd or Microsoft 365), it is stored with the check, along with whether a virus scanner looked at the message. ### Every Hop, Its Delay and TLS The Received headers become a list of hops with the delay at each one and whether it was encrypted, so a slow relay or a hop without TLS is named, not guessed. An alert for unencrypted hops is ready to turn on. ### A Fixed Test Message, Always Cleaned Up Subject 'WatchFor delivery check' plus a random token, a fixed body and an X-WatchFor-Probe header, so the monitor can't be used to send anything else. It deletes the message after reading it and sweeps leftovers older than an hour. ### Stage Timings for Both Sides SMTP connect, TLS, login and send on one side, mailbox login and search on the other, so a failed check says whether sending, delivery or the mailbox broke. ### Credentials Encrypted, Never Shown Both passwords are encrypted at rest, bound to that one monitor and never shown again: not in the dashboard, the API, MCP, exports, check results or logs. One login can serve both sides. ## A closer look Every hop, every stage, and only the verdicts the receiving server actually wrote. Each leg over time: a slow delivery shows apart from a slow login. Alerts for lost mail, spam placement, slow delivery and failed authentication. Send through your SMTP server, read back over IMAP or POP3. ## Why Test Delivery, Not Just the Server Every part of an email system can look healthy while mail goes missing. The SMTP server answers, the DNS records are correct, and messages still sit in a queue, get rejected by the next relay, wait out a greylist or land in spam after a key rotation. The only proof that the path works is a message that arrives. A round-trip monitor sends one on your schedule, from your own server to a mailbox you choose, and reads the headers the receiving side added. Pair it with SMTP and IMAP or POP3 monitors to see which side broke (the IMAP monitor also warns before the mailbox fills up and starts bouncing), an email policy monitor for the DNS records and a blacklist monitor for your server's reputation. [Start monitoring now](/auth/sign-up) A real message through your own SMTP server, with login Found over IMAP or POP3, in the Inbox or the spam folder Delivery time from accepted to arrived SPF, DKIM and DMARC verdicts from the receiving server Spam score and antivirus headers when the filter writes them Every relay hop with its delay and TLS Test messages deleted after each check, leftovers swept hourly Two failed deliveries in a row open the incident ## How Email Round-Trip Monitoring Works From your SMTP server to the mailbox and back to you 1 ### Connect the Sending Side Enter your SMTP host and the login your apps use to send, on 587 (STARTTLS) or 465 (implicit TLS). Port 25 is never used for sending. 2 ### Connect the Mailbox Enter the address to send to and its IMAP or POP3 server and login, or reuse the sending login. A mailbox kept for this test is best. Gmail needs an app password. 3 ### Send, Find, Delete At your interval (every 5 minutes at most), the probe sends the test message, waits up to 2 minutes for it by default, reads its headers and deletes it. 4 ### Get Alerts Message Not Delivered (critical) and Landed in Spam (warning) are on from the start. Slow delivery, SPF, DKIM or DMARC failures and unencrypted hops are ready to turn on. ## Email Round-Trip Monitoring Use Cases For mail that has to arrive, not just leave ### Password Resets and Sign-Up Emails If the reset email doesn't arrive, the user can't get in and support hears about it first. Send the test through the same SMTP login your app uses, to a mailbox at a big provider, and know when delivery stops or slows. ### After a Mail Migration or DNS Change A new provider, a new relay or a rotated DKIM key can quietly break authentication. The SPF, DKIM and DMARC results from the receiving server show it on the next check, not after the bounce reports. ### Your Own Mail Server Postfix or Exchange can accept mail and then sit on it behind a full queue, a stuck relay or a greylist. Delivery time and the per-hop delays show where it waited. ### Mail Between Two Platforms Send from one system and receive on another, such as your app's relay and your company mailbox, and watch the whole path, with every hop's TLS, as one monitor. ## Frequently asked questions Everything you need to know about email round-trip monitoring [All questions→](/faq)[Ask us directly](/contact) What is email round-trip monitoring? Email round-trip monitoring sends a real test message through your SMTP server on a schedule and checks that it arrives in a mailbox. It measures how long delivery took, whether the message landed in the Inbox or the spam folder, and what the receiving server concluded about SPF, DKIM and DMARC. Then it deletes the test message. How is it different from SMTP monitoring? What does the test message look like? Can it tell whether my mail lands in spam? Where do the SPF, DKIM and DMARC results come from? Which mail providers work? Why can't I send on port 25? How often does it run? How are the credentials stored? Which plans include email round-trip monitoring? ## From our blog Guides, deep-dives, and best practices from the WatchFor team [Email ### How to test email delivery end to end (and keep testing it) Oct 05, 2026·5 min readRead article](/blog/how-to-test-email-delivery)[Guides ### Late or in spam? How to read email headers with the Email Header Analyzer Oct 04, 2026·6 min readRead article](/blog/how-to-read-email-headers)[Email ### Why Your Emails Go to Spam (and how to fix it) Dec 02, 2025·3 min readRead article](/blog/why-emails-go-to-spam) ## Ready to Prove Your Email Arrives? Email round-trip monitors are on the Pro and Business plans. Sign up for free and upgrade when you add your first one. To check a single message by hand, paste its headers into the free email header analyzer. [Get started](/auth/sign-up)[View documentation](/docs/monitors/email-round-trip) --- Canonical page: https://watchfor.io/email-round-trip-monitoring · Site guide: https://watchfor.io/llms.txt