How can I restore my domain's reputation in Gmail?
This article explains the procedure by which the reputation of a domain can be restored in case messages are reaching or being seen as SPAM by GMail.
It frequently happens that you wait for an email, and it ends up delayed. Later you find out that it arrived but actually went into SPAM. You mark the email as NOT SPAM and move it to INBOX. However, the problem is not fully resolved. It is possible for GMAIL to repeatedly reject messages or worse, block them from the very first connection with their servers. When this happens, you receive a message with a rejection report that looks something like this:
Analyzing this report is quite difficult because GMail does not provide clear explanations regarding the reason for the rejection and an exact procedure for remedying the issue. GMail often encounters these situations, and the sent email, deemed suspicious to their servers, will automatically raise a red flag. The sender domain's reputation will suffer, including domains managed by G suite, and the sent messages will begin to be rejected. The domain's reputation is quite hard to restore, as when GMail starts rejecting messages, there is no option for recipients to mark as NOT SPAM and correct GMail's behavior.
The first step in trying to remedy the issue is obtaining more detailed reports by registering the domain in Postmaster Tools where delivery issues can be viewed. Messages are filtered based on content, subject, signature, and keywords written in the email. Consequently, the emails will need to be adapted to GMail's requirements, but that's not all. GMail's approach to email traffic is based on software that learns and analyzes trends and patterns in real time, correcting its own mistakes. The filters will adjust and adapt for each individual GMail user based on their behavior and will adapt to their preferences. If the majority of recipients do not open your emails or do not click on them at all, it will give GMail the impression that these messages are not important. Moreover, if someone marks the message as SPAM, GMail will categorize the domain as unsolicited. This combination of factors will lower the domain's reputation until it is completely blocked by the GMail server. Consequently, it is important to consider the content of the email and ensure that it is always viewed by the recipient.
Summarizing everything together, free email service providers try through various methods and technologies to maintain email traffic as legitimate by preventing SPAM, fraud-attempt emails, and other unwanted or unsolicited messages.