Host Monitoring: Choose the Right Monitor Type and Use It Well

What Host Monitoring Does

Host Monitoring watches specific endpoints instead of whole domains.

Use it when you care about a particular mail server, IP, hostname, HTTPS endpoint, or specific port and you want to know if it is reachable, healthy, and behaving the way you expect.

Where Domain Monitoring answers "is this domain's email authentication healthy?", Host Monitoring answers questions like:

• is this MX host reachable
• is SMTP still responding
• is the IP blacklisted
• is the certificate healthy
• is this specific port open

Before You Start

Before you create a host monitor, decide two things:

1. what you are monitoring
2. which monitor type matches that job

That choice matters because monitor type is fixed at creation time. You can edit the identifier, label, checks, and ports later, but you do not switch an existing SMTP monitor into an HTTPS or Port monitor.

Plans and Limits

Host Monitoring is available across plans, with larger limits and faster check schedules on paid tiers.

Each host monitor uses one slot. The sub-checks under a monitor (for example, SMTP connectivity + PTR + IP blacklist on an SMTP monitor) do not consume extra slots.

Choose the Right Monitor Type

mxio currently offers five host monitor types.

SMTP

Use an SMTP monitor for a mail server that should accept SMTP connections.

It is the right choice for:

• MX hosts
• outbound relays
• named SMTP endpoints you manage

SMTP monitors check:

• SMTP connectivity
• PTR / reverse DNS
• IP blacklist status

They default to monitoring port 25, with optional support for 465 and 587 in the port configuration.

IMAP

Use an IMAP monitor for a mailbox access server.

It is the right choice for:

• customer-facing IMAP servers
• internal mailbox endpoints

IMAP monitors check IMAP connectivity. The default port set includes 143 (standard IMAP) and 993 (IMAP over TLS).

HTTPS

Use an HTTPS monitor for a web endpoint where HTTPS uptime and certificate health matter.

This is useful for:

• webmail portals
• admin consoles
• support or status pages tied to your mail environment

IP

Use an IP monitor when you care about a specific IP address rather than a named service.

It is the right choice for:

• public mail IPs
• fixed infrastructure IPs
• addresses where blacklist status matters

IP monitors check:

• ping / reachability
• IP blacklist status

Port

Use a Port monitor when you want one question answered: is this port open on this host?

This is the most general option. It is useful for:

• custom services
• ports that are not part of the built-in SMTP or IMAP workflows
• quick connectivity monitoring without protocol-specific checks

Port monitors do not have extra sub-checks. They just test the selected port.

The Fast Version

The real setup flow is:

1. Open Add Host
2. Choose a monitor type
3. Enter the hostname or IP
4. Optionally add a label and adjust checks or ports
5. Create the monitor
6. Wait for the first check or click Check Now

Step 1: Open Add Host

Start from the Hosts section of the dashboard and click Add Host.

The add page opens with a type picker. This is the first important decision.

Step 2: Choose the Monitor Type

Pick the monitor type that matches the job.

Do not choose based only on the hostname. Choose based on what you want mxio to test.

Examples:

• mail.example.com that should accept mail: SMTP
• imap.example.com for mailbox access: IMAP
• status.example.com over TLS: HTTPS
• 203.0.113.10 for reachability and blacklist tracking: IP
• mail.example.com:2525 as a raw custom port check: Port

Step 3: Enter the Identifier

After you choose a type, enter the host identifier.

Depending on the type, that is:

• a hostname
• an IPv4 or IPv6 address
• a hostname plus a port number for Port monitors

You can also add an optional label such as:

Primary MX
Outbound relay
Webmail
Customer IMAP

Labels are there to make the list easier to scan later.

Step 4: Adjust Ports or Sub-Checks If Needed

Some monitor types expose more configuration.

SMTP and IMAP ports

SMTP and IMAP monitors let you control which protocol ports are tested.

That matters if:

• you only care about one port
• you run a non-default service mix
• you want to watch submission separately from classic SMTP

Sub-checks

Some monitor types run multiple checks under one monitor. For example, an SMTP monitor runs SMTP connectivity, PTR lookup, and IP blacklist checks together. An IP monitor runs ping and IP blacklist together.

You do not need to configure these individually — they come with the monitor type. The detail page shows results for each sub-check separately so you can tell exactly which part is healthy and which is not.

Step 5: Create the Host

When you click Create Host, mxio adds the monitor and opens its detail page.

At that point the host exists in monitoring. You do not need another activation step unless you later pause it.

Step 6: Run or Wait for the First Check

A new host often starts in an "awaiting first check" state.

That is normal. The detail page tells you this directly and gives you a Check Now button.

If you want immediate confirmation, click Check Now. Otherwise, the scheduled check will run automatically.

What Success Looks Like

A first-time user should expect this sequence:

1. the host appears in the Hosts list
2. the detail page shows the chosen monitor type
3. the first check runs automatically or after Check Now
4. sub-check results appear on the detail page
5. history and incidents begin building over time

If that is happening, the monitor is set up correctly.

Understanding the Dashboard

Hosts list

The main Hosts page shows:

• monitor type
• host identifier
• health status
• last checked timing
• bulk actions

Failures sort to the top so broken hosts stand out quickly.

Host detail page

The detail page is where the monitor becomes useful. It shows:

• current status
• check timing
• Check Now, Edit, Pause, and Activate
• sub-check results
• resolved IPs when the host resolves to multiple addresses
• trend history
• incidents
• activity timeline

This is the page you use when something looks off and you need detail.

Status states

The host states are simple:

Day-To-Day Use

If a host is healthy

You mostly leave it alone. mxio keeps checking on schedule and recording history.

If a host fails

Open the host and start with the failing sub-checks at the top. The detail page intentionally expands failing items first so you can see the problem without hunting for it.

If a hostname resolves to several IPs

The detail view can show multiple active resolved IPs. That matters for shared infrastructure, load-balanced services, and mail clusters. You are monitoring the endpoint as it resolves in practice, not just a single hardcoded IP.

If you need to stop monitoring temporarily

Pause the host. This keeps the object in the account without continuing active checks.

Host Monitoring and Domain Monitoring Work Together

These two features overlap, but they are not the same.

Use Domain Monitoring when you care about:

• SPF
• DKIM
• DMARC
• MX health
• delegation
• domain-level posture

Use Host Monitoring when you care about:

• a specific MX host
• a specific relay
• an IMAP server
• a TLS endpoint
• a particular public IP
• a single port

In practice, many teams use both:

• Domain Monitoring for policy and DNS health
• Host Monitoring for the infrastructure that actually answers on the network

Common Situations

You chose the wrong monitor type

Monitor type is a creation-time choice and cannot be changed afterward. If you need a different type, create the correct new monitor and delete or pause the old one.

You added a hostname and the IPs changed later

That is usually fine. Hostname-based monitors resolve at check time. If the service legitimately moved to different IPs, the monitor follows the hostname.

An IP is reachable but blacklisted

That is a real and useful state. Reachability and reputation are different questions. A host can be fully up and still have deliverability problems because of blacklist status.

You need to watch a custom service

Use a Port monitor if the service does not fit SMTP, IMAP, HTTPS, or plain IP monitoring cleanly.

Alerts

When a host check fails, mxio can notify you through your configured notification channels. Configure alert preferences in your account notification settings to control which check types trigger alerts and how they are delivered.

Alerts fire on state transitions (healthy → failing), not on every check cycle. You get one notification when something breaks and one when it recovers, not a flood of repeated alerts.

Best Practices

• Choose monitor type based on the check you need, not just the hostname format
• Use labels so the host list stays readable
• Click Check Now after major infrastructure changes
• Use SMTP monitors for actual mail hosts instead of generic Port checks whenever possible
• Use Domain Monitoring alongside Host Monitoring for the full picture

Related Articles

• Domain Monitoring: Setup, What It Checks, and How To Use It — the domain-level companion guide
• Fix a Blacklisted IP: Delisting, Root Cause, and Prevention — when reputation becomes the issue
• Missing MX Records — why MX health still matters at the domain layer
• Complete Email Authentication Guide — how the protocol side fits together