mail delivery delayed to gmail/gmail hosted domains

Dear Nanog'er,

Since about 4 weeks or more we experience a mail delivery delay (always between 03:09 and 03:10) to and gmail hosted domains.
We already filled out the "delivery problem report" but never heard something from them.

Are there any specs from google which explains when they delay mail acceptance?

We are not listed in any blocklists and the SPF, PTR record is correctly set.

Any ideas?