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Greylist questions

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    Posted: 22 January 2008 at 1:03pm
I was just introduced to the greylist. So far, it seems to be a great functionality.

Questions:

1. If I understand right, only the first time an email is sent to us is greylisted, on retry and all email followed from that IP will not be delayed since the IP will be listed in Greylist AllowList.

2. Is there any tool that I can use to get a list of SMTP servers for my customers - I do have all the email domains? I want to add them into our Greylist AllowList and white list or it's not necessary?

3. how can I adjust greylist limbo?


Edited by Stupid - 22 January 2008 at 1:19pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Desperado Quote  Post ReplyReply Direct Link To This Post Posted: 22 January 2008 at 4:08pm
 
Questions:

Q1. If I understand right, only the first time an email is sent to us is greylisted, on retry and all email followed from that IP will not be delayed since the IP will be listed in Greylist AllowList.
A1 . Correct until the "GreyListAllowedHold" expires and then the IP must go through the process again.

Q2. Is there any tool that I can use to get a list of SMTP servers for my customers - I do have all the email domains? I want to add them into our Greylist AllowList and white list or it's not necessary?
A2. Not necessary and really no provision to do so at this time.

Q3. how can I adjust greylist limbo?
A3. There are 3 settings in the SpamFilter.ini file.  The values in the [] are MY current values.
GreyListInterval=[420]   Time in seconds that an IP must wait until it is allowed to send after the initial connection.
GreyListLimboHold=[8]  Time in hours allowed for an IP to re-send and then be added to the allowed list.  If this time expires, the IP must start all over.
GreyListAllowedHold=[15]  Time in days that an IP is kept in the allow list.  After this time, it is removed and the IP must be authorized again.


Edited by Desperado - 22 January 2008 at 4:12pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Stupid Quote  Post ReplyReply Direct Link To This Post Posted: 22 January 2008 at 4:58pm
Are these in the documentation? What are the recommended values for these? Especially for the last one, GreyListAllowedHold=[15] ?

How long does an IP address stay in greylist limbo?

My emails (more than 10) sent from Yahoo Mail always have to go through the greylist. Is it because Yahoo changes its outgoing mail servers addresses all the time?


Edited by Stupid - 22 January 2008 at 5:35pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Desperado Quote  Post ReplyReply Direct Link To This Post Posted: 22 January 2008 at 5:45pm
 
The defaults are:
GreyListInterval=300
GreyListLimboHold=12
GreyListAllowedHold=90
 
If you change the values in the ini file they will change the next time the ini is reloaded by Spamfilter.
 
My personal recommendation for the Limbo is 8 as it is my belief that any properly configured mail server should have retried LONG before this expires.  It you set it too low, messages may never get delivered from some servers.
 
The setting GreyListInterval=300, is a judgment call between how long you want a real message delayed before it becomes trusted.  Yahoo is around 10 minutes (600) for example but that is too long for me which is why I set it to 480.
 
I feel the setting GreyListAllowedHold=90 is too long to trust any IP and I kept lowering it until my IP listing fell below 500,000 IPs as I really wanted it short but not so short as to constantly having to re-add the IP.  My experience is telling me that yahoo refreshes the data every day but I can not be sure.  I like my 15 day setting for now but I have my backup server set for 1 day.
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