The above warnings make your subscribers lose trust regarding your future emails, and might fail to open them and mark them as not spam. As this badly affects your email deliverability, we request you to take immediate actions.

How to avoid Gmail marking your emails spam due to suspicious URLs

The warning message shows that there's something suspicious in the URLs you used. So, focus on URLs and check that your sending practices follow the suggestions below.

• Check for broken URLs
  

  Always ensure your URLs work properly before including them in an email. Redirection to a non-existent page leads to abuse complaints from subscribers. 
  

• Blacklisted Domain
  

  URLs with blacklisted domains are a possible reason for the warning. Check if your URL domain and sender domain are blacklisted with anti-spam services such as Spamhaus, Spamcop, Barracuda, and others. If yes, then raise a de-list request to the service.
  

• Don't include URLs with multiple redirections
  

  Multiple redirections are a common trick used by spammers. When subscribers encounter multiple redirections, they feel insecure and mark the email as spam. So, make sure your URLs redirect straight to the desired page.
  

• Don't include shortened URLs from public services
  

  If the domain of a shortened URL is blacklisted, URLs are considered suspicious. So, avoid publicly available blacklisted URL shorteners.
  

• Don't seek subscribers' personal information 
  

  URLs should not be used to seek personal information such as email address, passwords, residential address, phone number, and credit card information.
  

• Avoid suspicious/spammy phrases in the URL or in the page redirected from the URL.
  

  Phrases such as "online dating", "lose weight", "please help", "extra income", and "donate" make your subscribers doubt the legitimacy your emails and mark them as spam.
  

• Send test emails to your Gmail account to identify if anything is wrong before sending the actual campaign.
  


• Maintain a proper WHOIS registry for your domain
  

  Spam filters check the WHOIS registry for anything suspicious. The information in the registry should be original and updated regularly.
  

Since URLs are the gateway to your click rate, it makes sense to optimize them. If your URLs appear safe in your future emails, Gmail eventually makes your emails appropriately land in the inbox.