All,
Yesterday we enabled IPv6 on all of our mail relays. Today we started noticing some delays on emails getting delivered in a timely manner (especially from Gmail). Looking at a few examples, it seems as though the root cause is related to the fact that Gmail is now preferring to send email to our IPv6 addresses and most of those addresses are new to our SQLGrey database. As an example, if you look at the headers, you might see something like the following:
X-Greylist: delayed 06:25:41 by SQLgrey-1.8.0
In this case, this email was delayed by over 6 hours before it was delivered. It seems as though Gmail isn’t retrying that often unfortunately and we are seeing these delays.
I’m going to continue to monitor the situation and also look into adding some exclusions for the Gmail IPv6 block (if one exists) for sqlgrey if this situation continues.
Thank you for your patience!
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Lance Albertson
Director
Oregon State University | Open Source Lab