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Re: Yahoo Mail Filtering

2010-07-31 16:30:59

On Jul 31, 2010, at 11:22 AM, Hector Santos wrote:

J.D. Falk wrote:

It's not the wikipedia definition of greylisting, but they do use 4xx 
replies to control the flow of inbound mail.

Ok, now I am starting to see 45x "grey listings", here is snap shot of a mail 


There are multiple retries spread across different machines.

Do you think they need the same exact IP or they support a class C
machine distribution?

Yahoo isn't greylisting.

"Yahoo is not keeping track of the mail it rejects and is not reliably allowing 
email through on the second attempt. There are a couple reasons why Yahoo is 
deferring mail.

        • Shedding load in a generic and non-specific way.
        • Shedding load by temporarily refusing mail from specific IPs.
In the first case, the shedding of load means nothing more than Yahoo is 
shedding load. There is not really anything the sender can do to compensate for 
this, nor is there any thing the sender is doing (except possibly send mail to 
Yahoo at the same time as the rest of the world) to precipitate the blocking."


Laura Atkins
Word to the Wise                        "The Deliverability Experts!"
Direct: 650 678-3454            Fax: 650 249-1909
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