Here at Constant Contact, we remain an industry leader in email delivery. This is no accident. Our delivery standards are designed to ensure the best possible reach for all of our customers.
That being said, it’s expected (read: absolutely normal) that most campaigns will have some level of bounces. Knowing the "why" behind them helps you ensure you are mailing to the cleanest, most engaged list possible. Today, we’re looking at the remaining categories: Mailbox Full, Vacation/Auto-Reply, and Other.
What is a Mailbox Full Bounce?
When an inbox reaches its maximum storage, it rejects the message and bounces it back to us as “Mailbox Full.”
If the recipient frees up space, will they start getting mail again?
Technically, yes. However, in 2026, we strongly recommend paying attention to our "Recommended for Removal" list. If a mailbox stays full for an extended period, it usually means the account has been abandoned. To ISPs, sending to abandoned accounts looks like poor list hygiene and can hurt your sender reputation. If they stay on this list, it's best to let them go.
What’s the deal with Vacation/Auto-Reply bounces?
You’re right to be curious! This is the exception to the rule. Messages in this category are actually delivered to the contact. We include them in the bounce report simply to let you know that you might not see an open or click from this person for a while.
Note: Most auto-replies go to your "Reply-to" address, but some mail servers are programmed to send them to your "From" address instead. If your personal inbox suddenly fills with "Out of Office" messages, that’s why!
What is the “Other” bounce category?
We sort bounces based on the technical codes the ISP sends back. If the information they provide isn’t specific (like a general "system error"), it gets sorted into "Other."
Should I remove my “Other” bounces?
It’s a judgment call. If a contact bounces as "Other" once, it might just be a temporary server hiccup. But if they bounce repeatedly, it’s a sign of a deeper issue. I recommend trying to verify their address through another channel. If you're sure the address is valid but it won't go through, reach out to our Support Team to investigate.
Where can I find these bounces?
Our reporting is now more interactive than ever:
Click the Reporting tab in your main menu.
Find your campaign and click the hyperlinked number under the Bounces column.
Use the All types drop-down menu to filter by Mailbox Full, Vacation, or Other.
Check the Recommended for Removal view to see which contacts are consistently failing to receive your mail.
Editor's Note: This article has been updated to reflect the latest Constant Contact features.
