Form emails not arriving

First, check the site's page (Manage) → Form messages. Every message is kept there, even if the email failed — nothing is lost.

If the message is there

Look at the small note next to the message's date:

• No note — the email was sent. Check your spam or junk folder, and add the sender to your contacts.
• "email not sent (…)" — the reason is in brackets. Often it's a wrong password or server setting in your own mail server settings.
• "sent via …" — your own mail server failed, so we sent it another way. The reason is shown.

Also check Settings → Send form messages to on the site's page — is the address right?

If the message isn't there

• Has the site been published since you added the form?
• Is the form connected? The Contact form block always is. Your own forms need the right Action and Method POST.
• Sent lots of test messages quickly? Each visitor can send 5 messages per 10 minutes.

Using Gmail?

Gmail needs an app password — your normal password won't work. See Sending form emails through your own email account.