Use MiaB to send as third-party forwarding email?

I have a permanent, third-party forwarding service that I like to use, and I would like my emails to appear as if they are “From:” that address. This seems legitimate to me, because it is an email address that was granted to me by the third party, and all email to it does forward to me. How do I set this up with MiaB? What follows is what I have tried so far.

For the discussion, let’s say that the third party address is “” and my MiaB is the nameserver and mail exchanger for domain

I set up an alias on my box of the form “ forwards to”. Sure, that puts a bunch of A and MX records for on, but who cares, nobody is asking about the IP addresses for
Once I have done that, my email client will happily send a message from with the smtp server using the username and password for my account on But the problem comes because they are DKIM signed with
DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple;;
s=mail; t=1478812475;
which is not a valid signature because I of course have no way of putting records on the real nameserver to match this signature. So now I have an invalid DKIM signature in my email, which is a huge spam no-no, and hence my messages are bounced from everywhere.
Interestingly, I can add as a “send from” address on a gmail account, and then the messages from via gmail come through with this header:
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=20130820;
and although they still get a small demerit for not being DKIM signed on the spam tester websites, they do not get marked as spam by most recipients because not being DKIM signed is a much less bad offense than having an invalid DKIM signature.

How can I configure MiaB to not generate DKIM signatures, or to change their headers like Google does, to be able to send email from via MiaB without their having invalid DKIM signatures?

Thanks for the help.

Generally, the best way to make it appear as if your email is from a third party is to actually route it through that third party. You can configure Postfix to do that, it’s called a satellite system. (MiaB doesn’t actually support that configuration, so you’ll be out in unsupported modification territory, but it’s at least doable).

And, since you call them a forwarding service, this sounds like it should be pretty easy.

If you can’t do that, then technically you can have your MiaB send the email directly… Problem is, you’re going to have deliverability issues since there’s no good way for recipients to tell your messages apart from spam. You’ll need to collaborate with your forwarding service.

If you still want to do that, you would start by managing your DNS externally (maybe through your ISP), and not including SPF/DKIM/DMARC records.

Sadly,’s explicit policy is to not let its registered users send outgoing mail through its servers; it merely forwards incoming mail to me. So I need to do the best I can to send the mails myself. What I’ve done at the moment is remove the forwarder from to in MiaB, and then manually edit the to remove the flag diallowing login-user/sender mismatch. That’s working OK, but yes, a few recipients are balking. Is there anything better than this that I can do?
Thanks, Glen

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