Re: Signing speed

From: A. Schulze <>
Date: Tue, 23 Jun 2015 21:48:55 +0200

Jamie Eckert:

> We are an ESP for a few clients and they are questioning our sending
> ability. Some of our clients have very large mailing lists. Our
> clients are wanting us to send about 100 to 200K per hour. I have
> been testing and I found that I can send up to 500k messages per
> hour from our software with no DKIM signing. When I turn on DKIM
> signing, I only get about 50k per hour. I understand it is doing a
> lot, but not sure what to expect. This may be the limitation, but I
> can't find anything on potential speed of signing outgoing messages.
> I am currently running CentOS 7 with Postfix and Opendkim. Any help
> would be great.

signing is heavy crypto work to do. You may vary the hash algorithm (
sha1 <-> sha256 )
and the signing key size ( 1024 bit or larger ... )
But I guess the keysize is not as important then the hash.

500k msg per hour equals to 138 messages per second. Assuming signing
one message take one second
you have 138 concurrent signing processes.

Last consider using hardware for crypto operations. But there is
virtually no known installation doing that.

Received on Tue Jun 23 2015 - 19:49:06 PST

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