Most mail servers implement spam filters to ensure that unsolicited emails do not get through. Spam filters read your emails and look for common elements associated with Spam. Filters scan for these traits in every email message. For example, they'll verify whether the message comes from the correct sender and that the 'From' address exists.
The filter also scans the contents of your message and assigns a spam score each time it comes across spam-like qualities. The spam score threshold is 5.0, but we advise you to keep this score under 2.5 if possible. Assess your spam score by using the Spam score tool when composing your email message. For example, using phrases like 'Click here!' or 'Specials!' might add 0.7 points to your score and using bright red fonts might add 2 points.
Once an email exceeds the threshold, it's classified as spam. Having a consistently high spam score with each email you send will negatively affect your sending reputation and some ISPs will eventually blacklist your mails.
Spam filters aren’t designed to detect whether spam was intentional or not so your message might still end up in the Spam/Junk folder if it contains certain keywords or has a high spam score. Follow these tips to avoid your email landing in Spam/Junk :