keybase.io sending emails via Amazon from IP explicitly disallowed by SPF

``` log
This is an email abuse report for an email message received from:
Source IP: 54.240.8.60
Timestamp: Tue, 22 Mar 2016 14:43:28 +0000

For more information about this format please see http://www.mipassoc.org/arf/.

Reasons why this email was rejected. Duplicate lines indicate multiple infractions such as multiple recipient attempts:

1: SPF designates your IP as a not-permitted source

Subject: @xxxx on twitter (your friend) just signed their account
From: "Keybase.io"
Date: 2016-03-22 14:42
To: david@blue-labs.org
```

And keybase.io explicitly disallows anything not listed here:

``` log
[david@Scott ~]$ dig +noall +answer -t txt keybase.io|grep -i spf
keybase.io. 104 IN TXT "v=spf1 mx include:_spf.google.com +a:mail1.keybase.io +a:mail2.keybase.io -all"

[david@Scott ~]$ dig +noall +answer -t a mail1.keybase.io
mail1.keybase.io. 300 IN A 54.84.192.51

[david@Scott ~]$ dig +noall +answer -t a mail2.keybase.io
mail2.keybase.io. 60 IN A 54.83.22.53
```

The source IP `54.240.8.60` is not in the approved sources list and `-all` is specified.

No repository file or test is named. Begin by reviewing the reported SPF record, approved mail hosts, and the Amazon source IP; done means the sending path is authorized by SPF or no longer sends from the disallowed source, with a verification of the resulting DNS and mail behavior.

Written by the indexing model from the issue text.