[exim] Delay by DomainKeys send

Hi, list!

A very strange problem!
If I send an E-Mail from a domain without DomainKeys Exim will try immediately
to deliver it.
If the domain uses DomainKeys, I see in the Logs, Exim wait 10-15 seconds
before proceed...

Here an example:

2007-06-15 14:53:34 1HzBJ0-0002ZP-Fo <= lucabert@??? H=(frodo.lucabert.intra) [KK.ZZ.YY.XX] P=esmtpa A=cram:omissis S=767
id=20070615145305.051d10dc@???
2007-06-15 14:53:48 1HzBJ0-0002ZP-Fo DK: message signed using a=rsa-sha1; q=dns; c=nofws; s=2007; d=lucabert.de; h=Received:Date:From:To:Subject:Message-ID:X-Mailer:X-Face:Mime-Version:Content-Type:Content-Transfer-Encoding;
2007-06-15 14:53:49 1HzBJ0-0002ZP-Fo => yyyyyy@??? R=external_gw T=remote_smtp_DK H=xxxxxxxx [XX.YY.ZZ.KK]
2007-06-15 14:53:49 1HzBJ0-0002ZP-Fo Completed

Now is the question: is it possible, that Exim needs 10-15 seconds to sign an E-Mail?
Please note: I don't use a C64 as Mail-Server! :)

Here is my router and transport:

My router:

external_gw:
driver = dnslookup
transport = ${if exists {/etc/exim/domainKeys/$sender_address_domain} {remote_smtp_DK} {remote_smtp}}
domains = ! +local_domains
no_more

my transport:

remote_smtp_DK:
driver = smtp
dk_canon = nofws
dk_selector = ${substr{0}{4}{$tod_zulu}}
dk_private_key = /etc/exim/domainKeys/$dk_domain/$dk_selector.priv

any idea?

Thanks a lot!

Luca Bertoncello
(lucabert@???)