Can't send emails to gmail addresses

[ducktopus]

Hello Community,

I'm trying to send an email to a gmail address from the online outlook (https://outlook.live.com/)  using my personal account. I get this in response:

mx.google.com rejected your message: *****@gmail.com (*****@gmail.com) Your message couldn't be delivered because the recipient's email server (outside Office 365) suspected that your message was spam. To fix this, try to modify your message, or change how you're sending the message, using the guidance in this article: E-mailing Best Practices for Senders. Then resend your message. If you continue to experience the problem, contact the recipient by some other means (by phone, for example) and ask them to ask their email admin to add your email address or your domain name (the text after the "@" symbol in your email address) to their allowed senders list.

[#2]

@ducktopus 

Did you try to send an Email to same gmail address with light content?

[#3]

@Kidd_Ip 

yes, I tried with a simple "can you get this" after the first one got rejected

[#4]

Google has been working to harden its DMARK, SPF, and DKIM validation. I would review your domain's DMARK, SPF, and DKIM records to ensure they reflect proper configurations. These DNS records will depend on whether you are sending from M365 directly or using a third-party email security tool.
You will likely continue to have issues sending emails to Google until you have proper DMARK, SPF, and DKIM records.