Gmail throttling?

Nathan Anderson nathana at
Sat Feb 22 12:55:37 UTC 2014

On Friday, February 21, 2014 4:59 PM, Eduardo A. Suárez <mailto:esuarez at> wrote:

> some of our users have forwarded the email to Gmail and Gmail now are
> complaining that this is bulk mail and delaying it.
> We have SPF, DKIM, DMARC, even SRS to try these things do not happen :(

Have you double-checked your setup to make sure it is performing SRS correctly?  In my experience, Google is secretly blacklisting certain IPs for unknown, unpublished reasons, and implementing SRS seems to be a surefire workaround.

If you aren't on the secret blacklist, mail will still pass even if it fails SPF, but once you are on the blacklist, mail that fails SPF (either softfail or fail) will not be delivered.  If a user of yours is forwarding mail from your server to Gmail, the SPF check is not going to be against *your* SPF record, but against the original sender's SPF record, and so the check will fail (since the message looks like it is coming from you, and your MX won't be listed in the original sender's SPF record...thus, it will look like you are spoofing mail for the original sender).  Adding a valid SPF record to your domain and then implementing SRS on your mail server should ensure that all SPF checks pass, even for mail that your users are forwarding to Gmail.

I wrote a post detailing my experience and findings:

Nathan Anderson
First Step Internet, LLC
nathana at

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