To prevent downtime while waiting for a response from a client, or the topic in an email needs to be discussed immediately (e.g. a bug), you should always call first before emailing.
Calling first can save valuable time versus waiting for someone to respond to your email, making you more productive.
It also saves time when discussing topics that are easier explained over the phone.
When you need to contact someone, the steps you should take are:
It’s rare for a client to complain about being contacted too often. What they will notice is if you only ever email. Don’t be afraid to call first before sending an email.