I am unable to reply to emails directly I have to start a whole new email to reply

Hello Kes,

Based on the "550 5.7.520 Message blocked because it contains content identified as spam" error, your reply emails are being flagged and blocked by the recipient's email server. This means the problem is not with your ability to initiate an email, but with something in your reply that is being misinterpreted by an external spam filter. 

Here are the most common causes and how you can fix them. 

Common causes and solutions

1. Content of the email

Spam filters analyze email content for common spam triggers, and in a reply, the quoted content from the original email is also included. 

• The fix: When you reply, try stripping the quoted history from the previous message and reply in plain text. This is one of the easiest ways to test if the issue is with the content of the email chain.
• What to watch for:
  • Suspicious links or images: If the email chain contains many links, especially from URL shorteners, it can increase the spam score.
    • Promotional language: Filters can be sensitive to phrases that look like marketing copy.
      • Formatting: Overly complex or messy HTML formatting can be flagged. 

2. Suspicious attachments

The email security systems of many providers, including Microsoft (which manages the sending server outlook.com in your error), are extra vigilant about attachments due to rising phishing campaigns. 

• The fix: Do not reply with the attachment included in the email chain. Instead, send the attachment separately in a new, unformatted email or share it via a cloud service like OneDrive. 

3. Issues with the recipient's server

Sometimes, the issue is on the receiving end. A strict or misconfigured spam filter on their side might be blocking your emails. This is especially likely if you can successfully reply to some addresses but not others. 

• The fix: There isn't much you can do on your end for this issue. You can let the recipient know that their server's spam filter is blocking your replies and ask them to add your email address to their "safe senders" list. 

4. Your sender reputation

Since you can initiate a new email but not reply, your overall sender reputation is likely fine, but it's not impossible for it to be a contributing factor. A "bad" domain reputation can sometimes get legitimate mail flagged. 

• The fix: As a regular email user, the best way to maintain a good sender reputation is to keep your email practices clean. Always ensure you only send emails to people who want to receive them. For an organizational email account, an IT administrator would need to check the domain's reputation with Microsoft. 

What you should do now

1. Test the Plain Text Reply. This is the fastest and easiest way to see if the issue is with the quoted content or formatting.
2. Contact the Recipient. Send them a new, separate email (which you said works) to let them know you are having trouble replying and have them check their spam filter settings.
3. Check Attachments. If any of the blocked emails contained an attachment, try sending a reply with no attachment and see if it goes through.

Regards,

Raviteja M.

Hello,

When you reply, use this instruction to convert the email to plain text, and let me know if it goes through.
https://support.microsoft.com/office/change-the-message-format-to-html-rich-text-format-or-plain-text-in-outlook-338a389d-11da-47fe-b693-cf41f792fefa