Why are Google Calendar invites being marked as junk in Office 365?

Marketer from Email Geeks explains that DMARC policy set to 'p=none' is not always harmless and can influence filtering. If the issue isn't universal, it's client-specific, suggesting investigation into the common email client, browser, or forwarding method.

Email marketer from Mailjet recommends several steps to take to ensure that calendar invites aren't being marked as spam. These are to ensure your sender information is accurate, regularly clean your email list and set a frequency for invites.

Email marketer from MXToolbox explains that if your domain or IP is on a blocklist used by Office 365, your calendar invites will likely be marked as junk. Regularly check your domain and IP against common blocklists.

Email marketer from Stack Overflow shares that the content of the .ics file itself can trigger spam filters. Includes suspicious URLs or phrases within the invite description can lead to junk mail classification.

Email marketer from SuperOffice shares that spammers use calendar invites because they often bypass traditional email filters. A high volume of invites from an unknown sender can easily be flagged as junk.

Email marketer from Small Business Trends shares that calendar invites can be used to send spam because some email providers treat them differently than regular emails. These invites can slip through email security checks and end up in the recipient's calendar, making them more visible and likely to be clicked on.

Email marketer from Litmus explains that a clean sending history is essential for good deliverability. A low sender reputation can cause email invites to be caught by spam filters. If the sender’s reputation is low due to spam reports, emails will be delivered to the junk mail folder.

Email marketer from Email on Acid explains that Office 365 uses a combination of factors, including content, sender reputation, and user feedback, to filter emails and calendar invites. A sudden change in sending patterns can trigger filters.

Email marketer from Reddit suggests ensuring proper domain authentication (SPF, DKIM, DMARC) is in place for the domain sending the calendar invites. Incorrect setup can lead to invites being flagged as spam by Office 365.

Email marketer from EmailVendorSelection shares that sending a large volume of calendar invites in a short period, especially to recipients who don't typically receive them, can trigger spam filters in Office 365.

Marketer from Email Geeks suggests that if only some users are affected with .ics files, there could be a common factor in their setup, such as increased spam filtering within the Outlook desktop client.

Email marketer from Microsoft Community responds that calendar invites might be flagged as junk due to the sender's IP address or domain having a poor reputation, even if the sender's email messages are delivered successfully.

Expert from Email Geeks suggests that heavy prospecting by the sending domains could be a factor, as those clients might have a poor reputation due to other activities.

Expert from Word to the Wise explains that it's important to establish good practices for calendar invites. This includes providing clear information about the event, avoiding misleading language, and ensuring recipients can easily unsubscribe or opt-out. Poor practices can lead to invites being flagged as spam.

Expert from Spam Resource details that calendar invites, like emails, are affected by sender authentication (SPF, DKIM, DMARC) and sending reputation. A poor reputation, due to spam complaints or blacklisting, can lead to invites being junked by Office 365.

Expert from Email Geeks asks if the issue is consistent across domains (e.g., affecting all of domain A and none of domain B). Also highlights that O365 expects authentication to align, regardless of a DMARC record.

Expert from Email Geeks highlights the issue of spam via calendar invites and the limited tools to combat it. Notes that an SCL of 5 from Microsoft indicates at least a 50/50 chance of being considered spam.

Documentation from Microsoft Learn explains that Exchange Online Protection (EOP) uses anti-spam policies to scan inbound messages (including calendar invites) for spam and malware. Admins can configure these policies to adjust filtering sensitivity.

Documentation from Google Workspace Admin Help specifies security settings and best practices for calendar invites, including ensuring that users are aware of potential phishing attempts through calendar invites. The documentation details that Google's security features help prevent spam.

Documentation from Microsoft Learn explains that Enhanced Filtering for Connectors in Exchange Online can improve the accuracy of spam filtering when email is routed through third-party services before reaching Office 365. Incorrect configuration can cause deliverability issues.

Documentation from Microsoft Learn details that the Spam Confidence Level (SCL) is a rating assigned to messages by EOP. Higher SCL values indicate a greater likelihood that a message is spam, leading to junk mail filtering.

Documentation from RFC Editor (RFC 5545) explains the iCalendar data format, which is used for calendar invites. It describes how the data should be structured within the .ics file. It states that incorrect formatting of the ICS file can cause issues with how the invites are delivered and received.