Troubleshooting Email Delivery, Possibly Setting up SMTP

We need help troubleshooting and fixing an issue with our email delivery for our website.

What we think happened:
We were using emails specific to our domain name: @elkmountaintents.com
For ease of use, we had the emails being forwarded to a personal email: @yahoo.com.
Our website was receiving spam comments that triggered many automated emails
Yahoo saw the bulk emails and concluded that @elkmountaintents.com was a source of spam and blocked emails. Clients with @yahoo email addresses could not receive emails, including order confirmations.
We tried to set our emails to come from @gmail.com but this didn't work; it seemed like it was actually using a system embedded in Wordpress.

We want all of our email correspondance to safely and effectively use the more professional @elkmountaintents.com addresses, and we don't want to run into this issue in the future.

We are not technology experts but wonder if setting up an SMTP may resolve the issue???

This job would entail:
*Reviewing previous techsupport emails
*Possibly talking to tech/server/hosting support
*Identifying the problem and finding a solution
*Implementing the solution
*Adjusting woocommerce, the "contact us" form, etc. to impliment solution
*Monitoring for 1 month to ensure everything is functioning correctly.