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Authentication-Results: [snip].mail.[snip].[snip].com; domainkeys=neutral (no sig);; dkim=neutral (no sig)
Received: from  (EHLO (
  by [snip ...]
Received: from ([]) by

Email from people who work at a company whose associated domain is "" is forwarded to a mail hosting company,"", via SMTP, and the email gets sent out by to the receipient. The IP addresses ( and ( are, of course, obscured here, and they are associated with, not with

If a header like the one above were received at a company with fairly strict mail filters, such as a major bank, would it typically get trapped or flagged by the filters as suspect, either as potential spam or phishing, or anything else? When dkim = "neutral (no sig) and domainkeys="neutral (no sig)" is that a sign to a strict filter than the email may be from a fly-by-night organization, so to speak?

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Whenever anyone asks about anti-spam techniques the answer is always "Maybe, maybe not. It depends". There is no one size fits all approach to sending email that never ever gets marked as spam because there is no one size fits all approach to filtering for spam. I could choose to filter email destined for my employer based on blocking all mail that continues the letter "D" somewhere in the sending domain should I wish. That would make me an idiot, sure, but there are lots of idiots out there sending and receiving email. – RobM Apr 29 '11 at 16:34
I realize that filters can employ arbitrary or idiosyncratic techniques, because programmers design them. But surely there must be "best practices" on which there is some consensus? – Tim May 2 '11 at 18:19
up vote 1 down vote accepted

DKIM is going to hold a lot less weight than other things, such as spf and PTR. Most likely, you will have no trouble.

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Thanks for the additional info of spf and PTR, and their importance relative to domainkeys and dkim. – Tim May 2 '11 at 18:21

Short answer is that it may not be blocked based on dkim=neutral alone.

But it is hard to say for sure, since they may or may not be using any number of filters. The only item to base an answer on is that your stating the assumption that they are use a "strict filter" whatever that is.

The best way to tell is to just send them an email and ask the email admins (or the recipient of email) to tell you why (or why not) your email did (or didn't) make it through the filter.

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"strict filter" I meant as a short-hand for "not letting email through if the sending organization has done little or nothing to aid in one's attempts to establish their bona-fides". – Tim May 2 '11 at 17:51

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