Googlebot wreaking havoc

This morning I wake up to emails saying that our Mailgun account has been disabled due to high volumes of email and high volumes of bounces. The logs indicate that way more emails have been sent than we had visitors. Emails are only sent as the result of a user clicking a link on the site, so I have no idea how this is possible.

After a few hours of investigation, it turns out Googlebot was crawling our site and kept following links and buttons that send emails. To prevent this from happening again I took a couple different precautions:

• Added rel="nofollow" to the links and buttons in question.
• Changed any link that generates an email from a GET to a POST
• Added meta robots tags to the pages in question with "nofollow"

Hopefully that will prevent this sort of thing from happening again.