v64 Bad Comcast IPv6 in Greylisting Causing Mail outage
This morning, I had several customers mention intermittent problems receiving emails on our v64 cPanel servers (yes still running Stable v64, until v66 arrives for Stable). When I looked in exim_mainlog, it was filling with errors like:
When using SMTP testing websites, many would report errors trying to connect (connection refused). In fact, from my own workstation, I received "421 Unexpected failure, please try later" when attempting to connect to port 25. After much troubleshooting, I finally narrowed it down to it "Comcast" being enabled under WHM > Email > Greylisting > Common Mail Providers. It seems that cPanel must have pushed out an auto update (which I have enabled) of this mail provider's IPs, and it included a badly formatted IPv6 IP. Unchecking TRUST next to Comcast and hitting Save instantly solved my problem. When we look at /etc/greylist_common_mail_providers, we see:
These are, apparently, not valid formatted IPv6 IP addresses. It seems that on v66 servers, this isn't a problem, for some reason. I've opened a ticket (Support Request ID 8847119) and will update this thread when I find out more. - Scott
2017-09-06 09:37:23 Internal error: invalid IPv6 address "2001:558:fe16:103:69:252:193::/112" passed to host_aton()When using SMTP testing websites, many would report errors trying to connect (connection refused). In fact, from my own workstation, I received "421 Unexpected failure, please try later" when attempting to connect to port 25. After much troubleshooting, I finally narrowed it down to it "Comcast" being enabled under WHM > Email > Greylisting > Common Mail Providers. It seems that cPanel must have pushed out an auto update (which I have enabled) of this mail provider's IPs, and it included a badly formatted IPv6 IP. Unchecking TRUST next to Comcast and hitting Save instantly solved my problem. When we look at /etc/greylist_common_mail_providers, we see:
"2001:558:fe16:103:69:252:193::/112" # Comcast
"2001:558:fe16:19:96:114:154:160/123" # Comcast
"2001:558:fe21:29:69:252:207::/121" # Comcast
"2001:558:fe21:30:162:150:58::/112" # ComcastThese are, apparently, not valid formatted IPv6 IP addresses. It seems that on v66 servers, this isn't a problem, for some reason. I've opened a ticket (Support Request ID 8847119) and will update this thread when I find out more. - Scott
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Here's a related thread: New Thread - Internal error: invalid IPv6 address 0 -
Thanks @Infopro -- apparently my cPanel forum search foo failed me! Sorry for the duplicate thread. Feel free to delete this thread if you wish. I can chime in on the other one. - Scott 0
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