--- title: IMAP Monitoring for Mail Servers and Mailboxes description: IMAP monitoring by WatchFor. Log in to a mailbox on a schedule, check TLS and the certificate, count messages, see how full the mailbox is and get an alert before it fills up or when mail stops arriving, confirmed from several locations. canonical: https://watchfor.io/imap-monitoring --- New # IMAP Monitoring: Know When Mailboxes Stop Working Port 993 answers, webmail loads, and nobody can log in. WatchFor logs in to a real mailbox over IMAP on every check and tells you which step failed. [Start monitoring mailboxes](/auth/sign-up)[See plans](/pricing) [IMAP monitor documentation](/docs/monitors/imap)[Email round-trip monitoring](/email-round-trip-monitoring) ## What an IMAP Check Tests The same steps a mail client takes, each timed and reported on its own ### A Real Login, Read-Only Each check logs in with the credentials you give it and opens the mailbox read-only, so nothing is marked as read, moved or deleted. Leave the username empty for a connection-only check of the greeting, TLS and capabilities. ### TLS and the Certificate Implicit TLS on 993 or STARTTLS on 143. 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 a plain connection the check notes whether the server offers a password login before encryption and whether STARTTLS is offered at all. The monitor itself never sends credentials over an unencrypted connection. ### Warned Before the Mailbox Fills Up A full mailbox bounces every new message, and the senders find out before you do. The check reads the server's quota (37.2 MB of 100 MB) and warns at 90 %, critical at 99 %. Message and unseen counts and the folder list (Sent, Drafts, Junk) come with it. ### Alert When Mail Stops Arriving The check reads the date of the newest message, never its subject or sender. No New Mail alerts when a mailbox that should receive something every day has gone quiet. ### Per-Stage Timings DNS, connect, TLS handshake, greeting, capabilities, login, mailbox open and folder list 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 Every stage of the IMAP session is timed, STARTTLS upgrade included. Each check keeps the greeting, capabilities, certificate and timings. Mail-specific rules: certificate, plain-text login, STARTTLS and new mail. Pick implicit TLS, STARTTLS or none; the port follows your choice. ## Why a Port Check Isn't Enough for IMAP Mailbox outages rarely look like downtime. Port 993 keeps accepting connections while the certificate has expired, an update has broken authentication, the server has stopped storing new mail or the mailbox is full and bounces everything new. People notice when their mail client asks for the password again, or when an expected message never shows up. An IMAP monitor does what the mail client does: it connects, negotiates TLS, logs in and opens the mailbox, and reports the step that failed. Failures are confirmed from several locations before anyone is paged. [Start monitoring now](/auth/sign-up) A real IMAP session: greeting, TLS, capabilities, login and mailbox Read-only: nothing is marked as read, moved or deleted Certificate validity and days left on every check, STARTTLS included A rule for servers that offer password login without encryption Newest-message age for mailboxes that should keep receiving mail Never miss mail because a mailbox filled up: quota alerts at 90 % and 99 % 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 IMAP Monitoring Works From mail host to alert in four steps 1 ### Add Your IMAP Server Enter the host name, such as imap.example.com, pick the TLS mode (implicit TLS on 993 by default) and choose the locations to check from. 2 ### Add a Login, or Don't A username and password test the login and the mailbox; a mailbox made for monitoring is best. 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, opens the mailbox read-only, lists the folders and reads the newest message's date, then logs out. 4 ### Get Alerts Certificate Expiry is on from the start; with a login, so are Login Failed and Mailbox Almost Full. An alert names the step that failed and the server's reply. ## IMAP Monitoring Use Cases For mailboxes people and systems depend on ### Your Own Mail Server Running Dovecot or Microsoft Exchange yourself means the certificate renewals, updates and disks are yours. An IMAP monitor catches the expired certificate or the broken login before the help desk does. ### Hosting Providers and MSPs One monitor per customer mail platform shows a problem on your side before the tickets arrive, and the stage timings tell a slow login from a slow network. ### Mailboxes That Must Keep Receiving A shared inbox for orders, support requests or form submissions shouldn't go quiet for a day, or fill up because nobody empties it. No New Mail alerts when the newest message is older than you expect; Mailbox Almost Full warns before customers start getting bounces. ### Certificates Outside Your Automation Mail servers are often left out of certificate automation. The certificate the IMAP server actually presents is checked on every run, on the STARTTLS port too, where an SSL monitor can't look. ## Frequently asked questions Everything you need to know about IMAP monitoring [All questions→](/faq)[Ask us directly](/contact) What is IMAP monitoring? IMAP monitoring connects to your mail server on a schedule and does what a mail client does: it reads the greeting, negotiates TLS, asks for the capabilities, logs in and opens a mailbox. You get an alert when any of those steps fails, when the certificate is about to expire, or when a mailbox stops receiving mail. Does the monitor read or change my email? How are my mailbox credentials stored? Does it work with Gmail and Microsoft 365? Which ports and TLS modes are supported? Can it alert me when mail stops arriving? Can WatchFor warn me before a mailbox is full? What is the mail server grade? Do I have to give it a login? Which plans include IMAP 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 IMAP Servers? IMAP monitors are on the Pro and Business plans. Sign up for free and upgrade when you add your first mail server. For the sending side, add an SMTP monitor; to prove mail arrives end to end, add an email round-trip monitor. [Get started](/auth/sign-up)[View documentation](/docs/monitors/imap) --- Canonical page: https://watchfor.io/imap-monitoring · Site guide: https://watchfor.io/llms.txt