Services for testing and finding errors in setting up DKIM?

Question

postfix

In one of my questions about blocking Yahoo mail of my clients with a large number of sent letters (clients are all from America)
habrahabr.ru/qa/17546/
Habra, the user mentioned that all mail services remove the limit on the rate of sending letters when using spf and dkim.
I decided to check it out, took an unused domain, attached spf to it, asked the client for a list of emails to send, and made a test mailing with the text test in the body and subject of the letter. spf definitely doesn't help send more emails.
I smoked bamboo for a couple of days and decided to get to dkim, so as not to break mail for current clients, I decided to experiment with dkim on micro instance from amazon.
I quickly installed postfix, dkim-milter, generated keys, configured milter, added milter to postfix, added the necessary keys to the dns records for the test domain.
I send a letter from the console to my gmail account and get
dkim=neutral (body hash did not verify) in the source of the letter.
I see that there is a dkim signature, I get the correct entries in dns through nslookup.
How to find out what is wrong?

Answer 1

The console script used extended headers to send a message, it is cured by adding
X-Header Yes
to the dkim-milter config,
if sent by telnet without extended headers, everything is signed correctly and without this line.
I checked that neither dkim nor spf affect the number of letters that can be sent to mailers within a certain time, it was precisely checked for yahoo.com with which clients mostly have problems.