A bounce occurs when a sent message is rejected by the receiving mail server. The most common causes for bounced email messages include a misspelled or nonexistent email address.
The first time a bounce, unsubscribe, spam report occurs, the email server reports this. Successive requests to addresses that already reside on these suppression lists (bounce, unsubscribe, spam) result in drops for their respective reasons. The email client adds these users to a 'Dropped' list to prevent emails being sent to that address and protect the reputation of 'email@example.com' with the respective email servers.
The most simple way to define spam in the Email world is by using these 2 words: unwanted email.
These are some of the most common reasons for which an email may end up in the Spam Folder and ways to avoid this:
- High complaint rate: If too many people are flagging mail as spam, ISPs will take action and will first start sending mail to the Spam Folder, then they may start throttling messages or even block them.
- High Frequency: This is the number one reason subscribers either hit the Spam Button or Unsubscribe from an email stream. ISPs want to make sure that their users’ mailboxes don’t get crowded and in order to protect their users from email fatigue they can start junking the messages.
- Sending to inactive users: People’s interests change all the time and so it happens with emails. Subscribers can lose interest and stop opening the emails. The most common tendency is to send emails to even more users. However, this will only hurt deliverability even more because ISPs have ways of monitoring the activity of the users. They can check whether users open the emails, click on links, and delete or mark emails as spam or not spam. Basically, they monitor the users’ level of responsiveness or engagement. Based on these metrics, ISPs decide folder placement - whether the email goes to the Inbox or if it gets Junked.
- Inadequate content: It is well known that the ISPs are protecting their users with the help of spam filters. Using the wrong words or even characters in an email can trigger the spam filters and therefore throw your email in the Spam Folder. The key thing to remember, is that a spam filter is trying to remove commercial advertisements and promotions. So generally, words that are common in such emails should be avoided or used sparingly.
When a user unsubscribes from a type of email being sent to them at the sender account level, SendGrid will suppress all of your attempts at sending this type of email to that user.