It can take some time while GMail pushes a mail through your GrayList. The reason is that Google has several SMTP outgoing mail servers. The problem is that Google is rotating these mail servers to send even a single mail. Another complication is that Google SMTP mail servers does not have a single IP but they rotate several IPs for a single mail server. All these together does not make a good friend with graylisting systems.

Google can sometimes cause headache if you have a GrayList system implemented on your mail server.

What Graylisting does is that it records tripples: IP + sender + receiver.

When an email is sent from GMail, it is temporarily refused by our mail server (code 450 or 451)

Aug 13 16:29:14 ns2 policyd: rcpt=170846, greylist=new, host=64.233.178.241 (hs-out-0708.google.com), from=somegoogleuser@gmail.com, to=somebody@yourdomain.com, size=0
Aug 13 16:36:21 ns2 policyd: rcpt=170872, greylist=new, host=64.233.184.235 (wr-out-0506.google.com), from=somegoogleuser@gmail.com, to=somebody@yourdomain.com, size=0
Aug 13 16:56:04 ns2 policyd: rcpt=170914, greylist=new, host=66.249.82.234 (wx-out-0506.google.com), from=somegoogleuser@gmail.com, to=somebody@yourdomain.com, size=0
Aug 13 17:29:50 ns2 policyd: rcpt=170982, greylist=update, host=64.233.184.231 (wr-out-0506.google.com), from=somegoogleuser@gmail.com, to=somebody@yourdomain.com, size=0

# host hs-out-0708.google.com
hs-out-0708.google.com has address 64.233.178.251
hs-out-0708.google.com has address 64.233.178.240
hs-out-0708.google.com has address 64.233.178.241
hs-out-0708.google.com has address 64.233.178.242
hs-out-0708.google.com has address 64.233.178.243
hs-out-0708.google.com has address 64.233.178.244
hs-out-0708.google.com has address 64.233.178.245
hs-out-0708.google.com has address 64.233.178.246
hs-out-0708.google.com has address 64.233.178.247
hs-out-0708.google.com has address 64.233.178.248
hs-out-0708.google.com has address 64.233.178.249
hs-out-0708.google.com has address 64.233.178.250

# host wr-out-0506.google.com
wr-out-0506.google.com has address 64.233.184.235
wr-out-0506.google.com has address 64.233.184.236
wr-out-0506.google.com has address 64.233.184.237
wr-out-0506.google.com has address 64.233.184.238
wr-out-0506.google.com has address 64.233.184.239
wr-out-0506.google.com has address 64.233.184.224
wr-out-0506.google.com has address 64.233.184.225
wr-out-0506.google.com has address 64.233.184.226
wr-out-0506.google.com has address 64.233.184.227
wr-out-0506.google.com has address 64.233.184.228
wr-out-0506.google.com has address 64.233.184.229
wr-out-0506.google.com has address 64.233.184.230
wr-out-0506.google.com has address 64.233.184.231
wr-out-0506.google.com has address 64.233.184.232
wr-out-0506.google.com has address 64.233.184.233
wr-out-0506.google.com has address 64.233.184.234

# host wx-out-0506.google.com
wx-out-0506.google.com has address 66.249.82.236
wx-out-0506.google.com has address 66.249.82.237
wx-out-0506.google.com has address 66.249.82.238
wx-out-0506.google.com has address 66.249.82.239
wx-out-0506.google.com has address 66.249.82.224
wx-out-0506.google.com has address 66.249.82.225
wx-out-0506.google.com has address 66.249.82.226
wx-out-0506.google.com has address 66.249.82.227
wx-out-0506.google.com has address 66.249.82.228
wx-out-0506.google.com has address 66.249.82.229
wx-out-0506.google.com has address 66.249.82.230
wx-out-0506.google.com has address 66.249.82.231
wx-out-0506.google.com has address 66.249.82.232
wx-out-0506.google.com has address 66.249.82.233
wx-out-0506.google.com has address 66.249.82.234
wx-out-0506.google.com has address 66.249.82.235
Graylisting and email comming from GMail

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