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Thunderbird Email Client Reports IP Address Temporarily Blacklisted
After I moved out of the area and switched to a different ISP, the Thunderbird client would not connect to Comcast. Thunderbird client reported that "comcast has temporarily blacklisted your IP address".
I spent hours working on this problem. I eventually found the solution.
I had to upgrade my own network (within the Unifi gateway) so that it would make use of IPv6. I also had to adjust parameters within Thunderbird, to ensure that it would actually IPv6. The forums previously had a thread on this issue (the temporarily blacklisted IP address), but the thread was closed. This still can be an issue. People should know to use IPv6 when possible,
The Problem: Many ISPs (like Cox) share a single "Public IPv4" address among multiple households or recycle them frequently. If one person on that IP sends spam, Comcast's security filters may "blacklist" that IP, blocking everyone else sharing it.
I spent hours working on this problem. I eventually found the solution.
I had to upgrade my own network (within the Unifi gateway) so that it would make use of IPv6. I also had to adjust parameters within Thunderbird, to ensure that it would actually IPv6. The forums previously had a thread on this issue (the temporarily blacklisted IP address), but the thread was closed. This still can be an issue. People should know to use IPv6 when possible,
The Problem: Many ISPs (like Cox) share a single "Public IPv4" address among multiple households or recycle them frequently. If one person on that IP sends spam, Comcast's security filters may "blacklist" that IP, blocking everyone else sharing it.
The Fix: Switch your connection to IPv6.
- Enable IPv6 on your Router: Ensure your router is set to "DHCPv6" or "Prefix Delegation" so it gets a unique IPv6 address from the ISP.
- Enable IPv6 in Thunderbird: Go to Settings > General > Config Editor and ensure
network.dns.disableIPv6is set to false. - The Result: Your computer will use its own unique, unshared IPv6 address to talk to Comcast. Since this address isn't shared with neighbors, you bypass the "IP Blacklist" meant for someone else.
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