Email spam, also known as junk email or unsolicited bulk email
A junk mail folder is a virtual inbox for storing ads and often unsolicited electronic mail.
Be sure to check it regularly and every few days you should check your spam folder to make sure no important email messages have accidentally been identified as spam.
Programs within e-mail generally include customization options to move unwelcome messages to a junk mail folder automatically, but often this mail needs to be manually moved to the folder after reaching an in-box.
When e-mail from an undesirable source comes through, typically there is a block list for logging the sender’s e-mail address or extension, subject field, or content keywords and having like messages sent directly to the junk mail folder.
Why are my emails going into recipients' spam folders?
Every recipient server is different and may apply different spam filtering criteria for the messages being received.
In most cases, recipient servers don't provide any information about spam filtering to the sender of an email that was filtered. It would give too much information to spammers who would use that data to get around spam filters.
Spam filters are constantly changing to adapt to new techniques and types of spam messages, so what lands in the inbox today could be spam filtered tomorrow. There are some things you can do to help ensure your emails are being delivered to the inbox.
Engagement
Most of the major email providers, including Yahoo!, AOL, Hotmail, and Gmail, use engagement-based filtering to help detect spam. This means that the more your recipients interact with your emails by opening, clicking, and reading, the more highly engaged your audience is, and the more likely you'll end up in their inboxes. If a lot of users are marking a message as spam, it's more likely to end up in other people's spam folders. If you've moved emails out of the spam folder, that's a positive indicator and can help ensure future emails that are similar are delivered to the inbox instead.
In addition to engagement, most spam filters use some kind of scoring mechanism to figure out how likely it is that an email is spam. If the email exceeds a certain threshold, it's filtered to the spam folder.
The threshold changes for every receiving server, and some are configurable by the recipients.
There are two major factors to consider when you find that your message is going to the junk, bulk, or SPAM folders.
- The Reputation of the Sender of Your Messages: DKIM , SPF , pTR records
- The Content of Your Messages
Checking your spam folder:
Every few days you should check your spam folder to make sure no important email messages have accidentally been identified as spam.
Marking an email as not spam:
If a real email message gets accidentally marked as spam, you can remove it from the spam folder by opening the message and clicking the "Not spam" button in the top menu bar. This will move the email message to your inbox where it will be safe.
Adding a Sender to Your Contacts: You are strongly encouraged to add the sender to your list of contacts. Doing so is an important step to reducing the likelihood of subsequent test emails from being sent to the ‘Spam’ folder.
Google has acknowledged this as a best practice: https://support.google.com/mail/answer/9008?hl=en
Google said:
If you find a message wrongly classified as spam, you can unmark the message. Just select the message, and click the Not Spam button that appears at the top and bottom of your current view. Unmarking a message will automatically move it to your inbox.
If you find that some senders’ messages are consistently being mislabeled as spam, you can prevent this by: Adding their email addresses to your Contacts list. Gmail will deliver messages from members of your Contacts list to your inbox, unless we know with high confidence that they are spam.
Addresses Not In The Contacts Enter Spam Folder: There are many times that auto-spam filter sends all messages from new senders to the spam folder even when they are legitimate senders. This has happened for many people and it is always advisable to add the address of a new friend, family or business associates into the contacts folder to prevent very important messages from being sent to the Spam folder.