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Network

FTP, IMAP, POP3, SMTP, and SSH

Check that your FTP, IMAP, POP3, SMTP, and SSH servers are reachable and answer with the expected greeting.

The FTP, IMAP, POP3, SMTP and SSH checks verify that a server is reachable and announces its service with the expected greeting. Each check opens a TCP connection to the configured targets, reads the server's first response, and compares its beginning with the greeting typical for the protocol. The checks run on the device with the octoja agent on Windows, Linux, and macOS (each in x64 and Arm64 builds), every 5 minutes by default. All five work the same way and differ only in their default port and expected greeting.

Prerequisites

Connections leave from the device the check runs on. Every target must be reachable from there, and any firewall in between must allow the relevant port.

Steps

  1. Open the device.
  2. Choose Checks → Add Check, then FTP, IMAP, POP3, SMTP or SSH.
  3. Enter the servers to probe under Targets (host or host:port) and adjust the other fields if needed.

To cover several devices, assign the check with a config package.

Protocols

CheckDefault portExpected greeting starts with
FTP21220
IMAP143* OK
POP3110+OK
SMTP25220
SSH22SSH-

Settings

FieldTypeRequiredDefaultDescription
Targets (host or host:port)list of stringsYes—Hostnames or IP addresses of the servers to probe, optionally with a port, e.g. mail.example.com:587. Without a port, the check uses the protocol's default port
Timeout (ms)integerNo5000Combined time allowed per target for connecting and receiving the greeting. Values outside 500–60000 are clamped
Greeting must contain (optional)stringNo—If set, the greeting must additionally contain this text, e.g. a server name or ESMTP. Matching is case-insensitive
  • A port is recognized only when the text after the last colon is a number from 1 to 65535. Otherwise the whole entry is treated as the host and the default port is used.
  • The check reads only the server's first response block. Set Greeting must contain (optional) to text from the first line of the greeting.
  • Up to ten targets are probed at the same time. Blank entries are ignored, and leading and trailing spaces are removed.

Results

Every target is graded on its own. The check reports the worst result across all targets.

Condition (per target)ResultShown as
Connected, the greeting starts with the expected text and, if set, contains the text from Greeting must contain (optional)OKConnection time in ms and the greeting
The greeting starts differently, lacks the required text, or the server sends nothing and closes the connectionCriticalUnexpected greeting
Connecting or receiving the greeting takes longer than Timeout (ms)CriticalConnection timed out
The hostname cannot be resolved or the connection is refusedCriticalConnection refused or unreachable
Unexpected error during executionErrorError message
No targets configuredWarningNo targets monitored.

Per target, the check reports:

  • Host and the port used
  • Whether the connection succeeded
  • The time to establish the connection in milliseconds
  • The server greeting, truncated to 200 characters
  • The result and, where one applies, the reason

Notes

  • The check does not negotiate TLS and does not log in. It evaluates only the unencrypted greeting. On implicit-TLS ports such as 993 (IMAPS), 995 (POP3S) or 465 (SMTPS), the server sends no greeting before the TLS handshake, so the check reports Critical for that target.
  • You can also assign the check to a network device. octoja then hides Targets (host or host:port), fills in the device's IP address on every run, and therefore always probes the default port. The network device's monitoring asset runs the check.

See also: Set up alerts for a check · Network Devices Reference

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