DKIM: Invalid signature record

Hi,

We are using SmarterMail 16.3.6989 and we are configuring DMIM using the default parameters:

dkimCanonicalizationAlgorithm_Body: relaxed
dkimCanonicalizationAlgorithm_Header: relaxed
dkimHashAlgorithm: sha256
dkimHeaderFieldOption: allnotspecified
dkimHeaderFields: return-path:received:comments:keywords:bcc:resent-bcc:dkim-signature

It works fine with gmail. However, with other servers it does not (e.g. Zoho and at least another one). Zoho by default does not accept the messages signed by SmarterMail. Zoho replies with:

Could not deliver message to the following recipient(s):
Failed Recipient: name@xpto.com
Reason: Remote host said: 554 5.2.3 MailPolicy violation Error delivering to mailboxes

We complain with zoho and the answer was that the sender domain (fkmotors.pt) fails DKIM validation.

We with listed the domain in Zoho and now we can see more details in the headers of messages:

DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
d=xpto.com; s=8d6a60b5130b8db;
h=content-type:mime-version:message-id:reply-to:date:subject:to
:from;
bh=iY...580=;
b=XO...0n
6M...vlF
ftW...Pk
Yp...AVY
7vq...V0
6Wp...9jLw==
......X-ZohoMail-DKIM: fail (Invalid signature record: Syntax error in field name: to
)

Does anyone has the same problem? Do you have any suggestions to solve this issue?

Thanks,

António

Employee Replied

3/15/2019 at 6:36 AM

Employee Post

António, can you verify in the matching sent items of this email message that the DKIM-Signature is all on one line. It is possible to split it into multiple lines as line as each line is preceded with a whitespace character (typically a space or a tab). Viewing it with in a notepad or other text editor with a fixed-width character font would help determine that. If this is not the case, then it would fail DKIM. If you have questions you can also send me a copy of the headers, and I can verify for you.

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