When a client's site goes down or an SSL certificate is about to expire, how fast you find out determines how bad the situation gets. A good monitoring tool is only as useful as the alerting system behind it. Get the alert to the wrong person, through the wrong channel, and it might as well not exist.

Here's a breakdown of the main alerting methods — email, Slack, and webhooks — and how to decide which to use for your agency.

Email alerts

Email is the default alerting method for most monitoring tools, and for good reason: everyone has it, it's persistent, and it creates a paper trail. When something breaks at 3am, an email sits in your inbox waiting when you wake up.

The main advantage of email is that it works well for non-urgent, advance-notice alerts. SSL expiry warnings sent 30 days out are a perfect fit — you don't need to wake anyone up, you just need a reminder that something needs attention in the next few weeks.

The main weakness is that email is easy to miss for urgent issues. If a client's site goes down on a Saturday afternoon and the alert lands in an inbox nobody checks on weekends, you've lost hours before anyone acts.

Best for: SSL expiry warnings, domain expiry reminders, weekly summary reports, and any alert where same-day response is acceptable.

Slack alerts

For teams that live in Slack, this is often the fastest alerting channel. A Slack message to the right channel is hard to miss, especially if you configure it to mention @channel or a specific person for critical events.

Slack's big advantage is team visibility. When an alert hits a shared channel, your whole team sees it at once. Nobody has to forward an email or remember to loop someone in — the information is already in front of everyone. This is particularly valuable for agencies where multiple team members might handle client issues depending on who's available.

Slack alerts also support threading, so a discussion about a specific outage can stay organized in one place.

Best for: Downtime alerts, SSL critical warnings (7 days or less), and any situation where you want team awareness rather than individual accountability.

Webhooks

Webhooks are the most flexible option. Instead of sending a message to a fixed destination, a webhook fires an HTTP POST request to any URL you specify — which could be a Zapier workflow, a PagerDuty integration, a custom internal tool, or anything else that can receive an HTTP request.

This makes webhooks the right choice for more complex alerting logic: routing alerts to an on-call rotation, triggering an automated remediation script, logging incidents to a project management tool, or sending SMS via a service like Twilio.

The tradeoff is setup complexity. Webhooks require something on the receiving end to process the payload, which means more configuration work upfront. For most agencies, email and Slack handle 90% of cases — webhooks are for when you need custom behavior those channels can't provide.

Best for: On-call rotations, integrating with existing tools (PagerDuty, OpsGenie, Zapier), automated responses, or any workflow that needs structured data rather than a human-readable message.

How to choose

Channel Speed Best use case Setup
Email Minutes to hours Advance warnings, audit trail Zero
Slack Seconds Team awareness, urgent issues One webhook URL
Webhook Seconds Custom workflows, on-call tools Requires receiver

Routing alerts to clients

One decision agencies often avoid but shouldn't: whether to copy clients on alerts. There are two schools of thought.

The first is to keep all alerts internal and fix problems before clients know about them. This works well if your team is responsive and issues rarely last more than a few minutes. The risk is that if something takes hours to resolve, the client experiences the problem without context — and the silence makes it worse.

The second is to route a copy of critical alerts to a client contact. This builds transparency and trust — clients appreciate knowing you're monitoring proactively and that they'll hear from you if something is wrong. For most agency-client relationships, this is the better approach for downtime alerts specifically.

For SSL expiry warnings, keeping alerts internal usually makes more sense. The client doesn't need to know you're renewing a cert — they just need it done.

The practical setup for most agencies

The goal is to make sure the right person knows within minutes, without creating so much noise that alerts get ignored. Start simple — email and one Slack channel — and add complexity only when the simple setup fails you.