HomeNewPandaSpam / Abuse TopicsValid email address bounced

14.10. Valid email address bounced

Updated 05.02.18

If you're using a Yahoo or AOL "from" email address with NewPanda, click here.

Several things can cause eMessages to valid email addresses to bounce.

The number one reason eMessages to valid email addresses bounce is that they are rejected by a SPAM filter or a firewall. These can live on the recipient's computer, in his his email firewall, or even in his ISP. SMTP notifications (Undeliverable notices) will usually contain a message like "Blocked" or "Unacceptable Content" or "Denied" to let you know "we saw it, but we're not letting it through for security purposes."

    What does that mean?  It means the eMessage contained content considered "spammy" by the 
    email server or individual settings in the recipient's email account. 

    How can I test this theory?  Try sending the recipient a plain-text eMessage (but be careful NOT TO
    USE the word "test" or any form thereof {testing, tested, tester} in the message or subject line).  If 
    your very simple and brief eMessage gets through, you can be relatively certain that something from
    your previous eMessage caused something on the recipient's side to bounce it.

Another possibility is that NewPanda's email server was blocked or blacklisted. This usually happens in cases where big old corporate email servers see a whole bunch of pretty much identical eMessages coming through from the NewPanda server, saying they're "from" you, and suspect we're up to no good. So they block us. 

Usually blocks are temporary, lasting from 2 to 24 hours. Other times, you have to ask (and we do stress, ASK) to be white-listed again. You may need to provide our range of IP addresses and servers:

    NewPanda's current IP address list can be viewed here.

    The domains associated with this range are:
           newpanda.com and

Sometimes the eMessages get through but land in the recipient's SPAM or Junk folder.  Be sure to have your recipients check those folders for your eMessages, and if necessary, add you and newpanda.com to their "safe senders" list or their address book. On rare occasions, other parameters or settings over-rule the safe senders list or address book contacts.

Or it's possible that your recipient's email box was full. NewPanda tries to deliver your message over a several-day period in these cases, but after a certain number of attempts, we will stop trying in order to not make the Email Service Provider suspect we're trying to spam your recipient.

Finally, your message may be getting 100% blocked by a major ISP (like AOL, Comcast, etc.). NewPanda has set up feedback loops with the major ISPs to mitigate instances of temporary blocks, but once in a while, despite our best efforts, a user will send so many eMessages that throw flags that we'll inadvertently be blocked. These issues are almost always temporary (from a few hours to a day or two) and are always automatically lifted (manual intervention is not possible) at the end of the temporary block period. 

In cases where an entire message is blocked, if you've created the message yourself, check it very carefully for spammy content (if we created the message, we've designed it for maximum deliverability, and we have thoroughly tested it). If you're the culprit, you'll have to revise your eMessage before you resend it. Also please let us know right away, no matter what the cause. We'll contact the ISP if we can, and we'll investigate the cause of the block in case someone is violating our Terms of Use and needs to be temporarily or permanently shut down.

Regardless of the reason, if a particular recipient's email bounces too many times in a row, we must permanently remove them from our "send" list. This is done so the Email Service Providers out there (your recipients' email accounts) won't get too many "rejections" from NewPanda's servers and permanently block us (and when we say US, we mean all of YOUR messages).  Our good standing in the Email community is based partly on the number of messages that go through our servers that are undeliverable and/or get blocked. We have a three-strike policy in order to protect our integrity and the deliverability of all of our customers' messages.

Have a valid email address that bounced? Click here for instructions on clearing bounce records for valid email addresses.

Related Pages
This page was: Helpful | Not Helpful