The short answer
To be sure a form still delivers, something has to submit it and check that the email arrives. Uptime monitors and email-log plugins each cover part of the path; a daily end-to-end test covers all of it. SubmitCanary does that for one Contact Form 7, WPForms or Fluent Forms form, free during the beta.
| What is checked | Testing by hand | Uptime monitor | Email-log plugin | SubmitCanary |
|---|---|---|---|---|
| Page loads | When you remember | Yes, often every few minutes | No | Daily |
| Form is present and submits | When you remember | No | No | Daily |
| WordPress hands the email to the mail server | Indirectly | No | Yes, every email | Daily |
| The email actually arrives in an inbox | In your inbox | No | No | In a dedicated test inbox |
| Tells you which step broke | If you investigate | Page only | Send step only | Yes: page, form, submission or email |
| Noise in the client's inbox | A test email each time | None | None | None: tests go to the test inbox |
Testing by hand
Free and catches everything on the day you do it, but forms usually break silently between tests, after a plugin update or a mail change. Most people stop testing after launch.
Uptime monitors
Tools such as UptimeRobot are the right choice for knowing when the whole site is down, and they check far more often than once a day. They do not fill in or submit the form, so a broken form or a failing mail setup stays invisible.
Email-log and alert plugins
Plugins such as WP Mail SMTP record every email WordPress tries to send and can alert you when the hand-off to the mail server fails. They are worth having alongside a monitor. They work from inside the site, so they cannot tell you when the form itself no longer submits, or confirm that a message arrived.
SubmitCanary
Once a day it submits one clearly labelled test through your form, from outside like a visitor, and confirms the email reaches a dedicated test inbox. If a step fails you get one email naming it, and another when it recovers. It is deliberately narrow: one simple form per site, no CAPTCHA bypass, and it does not prove placement in your client's own inbox. Other form monitors cover more form builders, CAPTCHA forms or checkouts; SubmitCanary focuses on doing one test safely and stating its limits.