You are a Gmail user and is waiting for an important email, but haven’t sent yet after a couple days of waiting. When you check the Spam folder, the email evidently appears there then you want to mark it as not spam and prevent emails from the same sender from going to Spam folder again.
Gmail actually has a good spam filter, but nothing is perfect. Gmail is no exception.
If you want to stop emails sent from certain senders from going to Spam folder in Gmail, you can take advantage of the filter feature offered by Gmail.
First off, login to Gmail and go the Settings menu.
On the Settings page of gmail, click the Filters and Blocked Addresses tab and click the Create a new filter link.
A pop-up form will appear. Enter the email address you want prevent from going to Spam on the From field. Separate with comma if you want to enter more than one email addresses. Once you are done entering the email addresses, click the Create filter with this search link on the bottom-right corner of the pop-up.
On the next page on the pop-up, check the Never send it to spam option and click the Create filter button.
That’s it. Starting now, you should see the emails sent from the sender you have filtered on the Inbox folder instead of Spam.