GSuite - User suspended for spamming alert
We know it looks concerning, but it's actually a fairly benign alert at the GSuite level. When a lot of emails suddenly come from an account, GSuite will proactively lock the account.
Dover has taken steps to mitigate this over time by rate-limiting emails that are sent out, so this occurs rarely.
As an admin, you should be able to go to the Alert Center and unblock the account. This shouldn't compromise on your domain's deliverability or spam issues as it is an internal GSuite mechanism.