To "bypass" or somehow defeat greylisting, you mean?
I'm not aware of any via workarounds, no. I would certainly be interested in hearing about any , though, since I use greylisting on mail servers with thousands of users.
In some cases, such as when using OpenBSD's spamd , you (an SMTP client) don't even get to talk to the "real" SMTP server until you've successfully "passed the tests". This is the primary implementation of greylisting that I use, FWIW.