Starting February 1, Gmail and Yahoo introduced new requirements for all emails to improve deliverability and reduce spam. The Gmail policy applies only to senders who send more than 5,000 emails a day to Gmail users. This probably does not concern 99% of people reading this email, but I recommend that everyone adhere to this policy as a best practice to avoid any issues with your marketing emails being delivered. Here are some things you can do:

Send emails from your own domain (e.g., yourcompany.com) and not from a free email address like gmail.com or yahoo.com.
Make unsubscribing easy. All popular email marketing systems facilitate this; however, if you send over 5,000 messages daily, you must include a one-click unsubscribe option.
Avoid being flagged as spam. If your recipients mark your emails as spam beyond a certain threshold, your deliverability to Gmail and Yahoo accounts could be affected. This means not purchasing email lists or adding people to your list without their permission.

The next two requirements may seem technical but take only a few minutes to implement. Your marketing email provider will have instructions on how to do this, and some, like MailChimp, offer automated tools that simplify the process.

Authenticate your domain using CNAME records.
Publish a DMARC policy record in your DNS settings.

This might seem complicated, but taking these steps increases the likelihood that your marketing emails will reach your intended recipients now and in the future.