Why is my first email broadcast going to spam/junk?

When you send email broadcasts from a new subdomain, mailbox providers (like Gmail, Outlook, Yahoo) don’t know whether that domain is trustworthy yet. To protect users from spam, they treat new sending domains with caution and as a result, early sends may be filtered to spam while your subdomain builds a sending reputation. This is expected behavior during the warm up process.

Email providers evaluate new senders based on behavior that develops over time, including:

1. No existing sending reputation

A new subdomain has no historical data. Until providers see consistent sending patterns, they may limit inbox placement. This can be true even if your root domain has a reputation to it (positive or negative). 

2. Sudden or high sending volume

Sending too many emails within a broadcast too quickly from a new subdomain can look suspicious. Gradual volume increases help providers trust that the traffic is legitimate.

3. Engagement is still forming

Mailbox providers track how recipients interact with your email broadcasts:

• Opens
• Clicks
• Replies
• Deletions
• Unsubscribes
• Spam Complaints

This is why warming up matters! Warming up a subdomain means sending email broadcasts slowly and consistently, starting with smaller volumes and gradually increasing over days or weeks based on performance monitoring until you reach your full audience. This helps mailbox providers see that your email broadcasts are wanted by recipients, engagement is positive, complaint rates are low, and sending behavior is predictable. Inbox placement typically improves once these pillars are met. You can read more about warming up here.