--- title: POP3 Monitoring for Mail Servers description: POP3 monitoring by WatchFor. Check the greeting, TLS and certificate, the login and the mailbox size of a POP3 server on a schedule, and get an alert when mail stops arriving. canonical: https://watchfor.io/pop3-monitoring --- New # POP3 Monitoring for the Mailboxes Your Systems Collect From When a POP3 login breaks, nothing looks down: the help desk, the order importer or the scanner inbox just stops picking up mail. WatchFor logs in on every check and tells you which step failed. [Start monitoring POP3](/auth/sign-up)[See plans](/pricing) [POP3 monitor documentation](/docs/monitors/pop3)[IMAP monitoring](/imap-monitoring) ## What a POP3 Check Tests A real POP3 session, each step timed and reported on its own ### A Real Login, Nothing Downloaded Each check logs in with the credentials you give it, reads the mailbox status and logs out. No message is downloaded or deleted. Leave the username empty for a connection-only check of the greeting, TLS and capabilities. ### TLS and the Certificate Implicit TLS on 995 or STLS on 110. Every check records the TLS version, verifies the certificate chain and host name, and counts the days left. Certificate Expiry warns 14 days ahead by default. ### Password Login Without Encryption On port 110 the check notes whether the server offers a password login before encryption and whether STLS is offered at all. The monitor itself never sends credentials over an unencrypted connection. ### Mailbox Size, With Your Own Limit The number of waiting messages and the mailbox size on every check. POP3 has no quota command, so you set the limit: Mailbox Size alerts when the mailbox passes it, before a full mailbox starts bouncing mail. A mailbox that only grows usually means the collector has stopped. ### Alert When Mail Stops Arriving The check reads only the headers of the newest message to get its date, never the body, and stores only the age. No New Mail alerts when a mailbox has gone quiet for longer than you expect. ### Per-Stage Timings DNS, connect, TLS handshake, greeting, capabilities, login, STAT, UIDL and TOP are timed separately, so a slow login looks different from a slow network. ### Mail Server Grade A grade from A+ to F from the TLS version, certificate, encryption mode, plain-text login and response time, with the reasons listed under it. No encryption, or a certificate that isn't trusted, is an F. ### Credentials Encrypted, Never Shown The password is encrypted at rest, bound to that one monitor and never shown again: not in the dashboard, the API, MCP, exports, check results or logs. Leave it blank when editing to keep it. ## A closer look Each check keeps the greeting, capabilities, certificate and timings. Separate rules for the certificate, plain-text login, STLS and slow checks. Implicit TLS on 995 or an upgrade on 110; the port follows your choice. ## Why Watch a Protocol Most People Have Forgotten POP3 is rarely what a person opens in the morning. It is what a help-desk tool, a ticketing system, an order importer or a scan-to-email workflow uses to collect mail in the background, often from a mailbox nobody looks at. When the login breaks after a password rotation or the certificate expires, those systems fail quietly and the mail piles up. A POP3 monitor logs in the way they do and alerts on the failed step, the certificate, and a mailbox that keeps growing or stops receiving. Failures are confirmed from several locations before anyone is paged. [Start monitoring now](/auth/sign-up) A real POP3 session: greeting, TLS, capabilities, login and STAT Nothing downloaded or deleted Certificate validity and days left on every check, STLS included A rule for servers that offer password login without encryption Message count, mailbox size and newest-message age A size alert at the limit you choose, before a full mailbox bounces mail A mail server grade from A+ to F, with the reasons Passwords encrypted at rest and never shown again Alerts on any of 16 channels, including email, Slack and PagerDuty ## How POP3 Monitoring Works From mail host to alert in four steps 1 ### Add Your POP3 Server Enter the host name, such as pop.example.com, pick the TLS mode (implicit TLS on 995 by default) and choose the locations to check from. 2 ### Add the Login Your System Uses Use the same mailbox the collecting system reads, or one made for monitoring. Gmail needs an app password. Without a login the check covers the connection, TLS and capabilities. 3 ### Monitor 24/7 At your interval, a probe connects, completes TLS, logs in, reads the mailbox status, gets the newest message's date from its headers and logs out. 4 ### Get Alerts Certificate Expiry, and Login Failed when you add a login, are on from the start. An alert names the step that failed and the server's reply. ## POP3 Monitoring Use Cases For mailboxes that something collects from ### Help Desks and Ticketing Systems Support tools that turn email into tickets often collect over POP3. If the login fails, customer emails sit unanswered while the tool looks healthy. Monitor the same mailbox with the same login. ### Order and Invoice Importers Scripts and ERP connectors that read orders, invoices or reports from a mailbox stop silently. A growing mailbox size or a failed login is the first sign. ### Hosting Providers Customers still configure POP3 in desktop mail clients. One monitor per mail platform shows a login or certificate problem on your side before the support calls start. ### Legacy Devices and Applications Older software that only speaks POP3 keeps working until the server's TLS settings or certificate change under it. The grade and the TLS version show what each check negotiated. ## Frequently asked questions Everything you need to know about POP3 monitoring [All questions→](/faq)[Ask us directly](/contact) What is POP3 monitoring? POP3 monitoring connects to your mail server on a schedule and does what a POP3 client does: it reads the greeting, negotiates TLS, asks for the capabilities, logs in and reads the mailbox status. You get an alert when a step fails, when the certificate is about to expire, or when a mailbox stops receiving mail. Will the monitor download or delete messages? How are my mailbox credentials stored? Does it work with Gmail and Microsoft 365? Which ports and TLS modes are supported? Should I use the POP3 or the IMAP monitor? Can it warn me before the mailbox is full? What is the mail server grade? Which plans include POP3 monitoring? Can I monitor internal or private mail servers? ## From our blog Guides, deep-dives, and best practices from the WatchFor team [Email ### IMAP and POP3 monitoring: how to know when a mailbox stops working Oct 05, 2026·6 min readRead article](/blog/imap-pop3-monitoring)[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 ### Are TLS 1.0 and 1.1 really off? How to check with the TLS Version Checker Oct 04, 2026·6 min readRead article](/blog/how-to-check-tls-versions) ## Ready to Monitor Your POP3 Servers? POP3 monitors are on the Pro and Business plans. Sign up for free and upgrade when you add your first mail server. To prove that mail sent to that mailbox actually arrives, add an email round-trip monitor. [Get started](/auth/sign-up)[View documentation](/docs/monitors/pop3) --- Canonical page: https://watchfor.io/pop3-monitoring · Site guide: https://watchfor.io/llms.txt