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mrralan

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For those of you ussing an SMTP greeting delay, I'm curious how long most people have their's set. I have mine at 25 seconds but I'm thinking of lowering it a bit.
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campodoro74

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Mine's on 16 seconds.
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marook

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15 sec.

It shoudl be between 13-30, but 15-25 is said to be best. Stops a Huge part of spam here!

Regards,

Jakob Peterhänsel
Consultant - Humac A/S

Apple Certified Support Professional (ACSP)
Apple Certified Technical Coordinator (ACTC)
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troxell

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I started at 20sec and had clients who could not email us, dropped to 15 then 7 then turned it off Sad
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marook

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Well, it would be much better to put those few servers in the whitelist - but they should run a server that allows the wait time! Everything else is bad.
The reason for this to wok agains spammers, is that they don't have time to wait, if they have to deliver millions of mails each day.

Regards,

Jakob Peterhänsel
Consultant - Humac A/S

Apple Certified Support Professional (ACSP)
Apple Certified Technical Coordinator (ACTC)
AppleSeed/CQF member since 1998
Kerio Messaging Partner
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troxell

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Unfortunately we have thousands of potential clients emailing us from unknown servers. Many would never bother again if we didn't respond the first time. I feel I had no choice. Crying or Very Sad Just try explaining to a sales manager that he lost a lucrative prospective sale because we were try to keep some spam out.
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sonofcolin

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Quote:
I started at 20sec and had clients who could not email us, dropped to 15 then 7 then turned it off

That sounds most odd to me! I've never seen that. Even if a mailserver drops the connection after 20 seconds, it will keep re-trying. Most servers will not drop a connection until after 30 seconds.
I'm curious as to how you know that the sending server is dropping the connection? Are you watching this process in real time?? Are you getting logs from the sending server admin which shows this?
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pcunix

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I have to agree with sonofcolin. I've only had ONE instance of trouble with this and that was not a legitimate mailserver - it was some device that used smtp directly and couldn't be reprogrammed either to do it correctly. It was probably some piece of junk scripting written many years ago, but the customer needed to get mail from it and that was that. Other than that, I've never seen a problem.

Tony Lawrence
Kerio Preferred Partner and Reseller
Certified for Connect, Control
http://aplawrence.com
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GlennK

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15 here. Any longer and people will start to notice a big delay when sending from IPs not in the "local clients" list.
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troxell

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Yes, those servers keep trying. So the sender gets a delay response. But that just exasperates the issue as most recipients read a delay email as failed email, despite having been explained the difference between delayed and failed.

...and when their server tries again it fails for the same reason it did the first time, timeout.

Yes, I did indeed watch in real time and many equivalents in the logs.

Remember, you only know about the email you missed if the sender proactively calls you. (with prospective clients...rare)

If they never bother, you go on blissfully believing the system is working wonderfully.

Imagine the scenario...a Purchasing agent sends us and our competitors a Quote Request. ...and never hears from us.

Do they call us? ...or too often to be ok, do they buy from the other guy and soon scratch us off their list of vendors?

Hopefully you see the dilemma.

Many thousands of clients whose systems we can't control.

For us anyway... "SMTP Greeting Delay" is a wonderful idea that didn't work in the (our) real world Sad
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sonofcolin

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It appears that the MTA's you are having trouble with are not RFC compliant:
Quote:
RFC 2821
Based on extensive experience with busy mail-relay hosts, the minimum
per-command timeout values SHOULD be as follows:

Initial 220 Message: 5 minutes
An SMTP client process needs to distinguish between a failed TCP
connection and a delay in receiving the initial 220 greeting
message. Many SMTP servers accept a TCP connection but delay
delivery of the 220 message until their system load permits more
mail to be processed.

MAIL Command: 5 minutes

RCPT Command: 5 minutes
A longer timeout is required if processing of mailing lists and
aliases is not deferred until after the message was accepted.

DATA Initiation: 2 minutes
This is while awaiting the "354 Start Input" reply to a DATA
command.

Data Block: 3 minutes
This is while awaiting the completion of each TCP SEND call
transmitting a chunk of data.

DATA Termination: 10 minutes.
This is while awaiting the "250 OK" reply. When the receiver gets
the final period terminating the message data, it typically
performs processing to deliver the message to a user mailbox. A
spurious timeout at this point would be very wasteful and would
typically result in delivery of multiple copies of the message,
since it has been successfully sent and the server has accepted
responsibility for delivery. See section 6.1 for additional
discussion.

An SMTP server SHOULD have a timeout of at least 5 minutes while it
is awaiting the next command from the sender.

Quote:
I started at 20sec and had clients who could not email us, dropped to 15 then 7 then turned it off

Might be worth mentioning to those clients that they need a new server admin who knows what they are doing Wink
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elias

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troxell wrote on Sun, 04 April 2010 12:07
For us anyway... "SMTP Greeting Delay" is a wonderful idea that didn't work in the (our) real world Sad

If you can't set that delay to something reasonable like 15 seconds without having mail delivery problems, then you likely have some other issue. You should double-check your DNS settings to make sure your server has good DNS servers configured that are working and reply quickly. Also make sure you don't have any RBLs configured that are no longer functional that would cause lookups to time out.

At 7 seconds, the chance of missing legitimate mail as a result of that delay is essentially zero. You have something else happening that you're probably not aware of which you'll want to track down asap. You're at a far greater risk of losing legitimate mail from that problem than you are with a reasonable SMTP Greeting Delay setting.

-Elias

[Updated on: Sun, 04 April 2010 23:22]

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troxell

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elias wrote on Sun, 04 April 2010 14:20
troxell wrote on Sun, 04 April 2010 12:07
For us anyway... "SMTP Greeting Delay" is a wonderful idea that didn't work in the (our) real world Sad


At 7 seconds, the chance of missing legitimate mail as a result of that delay is essentially zero. You have something else happening that you're probably not aware of which you'll want to track down asap. You're at a far greater risk of losing legitimate mail from that problem than you are with a reasonable SMTP Greeting Delay setting.

-Elias


Good point, I will take a deeper look.
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pcunix

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troxell wrote on Sun, 04 April 2010 15:07
Yes, those servers keep trying. So the sender gets a delay response. But that just exasperates the issue as most recipients read a delay email as failed email, despite having been explained the difference between delayed and failed.




No, not from the greeting delay.

A proper MTA will wait for the greeting.

An improper MTA (almost always a spammer) will not wait, will start blasting its message, and be rejected.

No MTA should see the delay as cause for thinking your server is not ready. Even without you setting this, they'd sometimes see delayed responses.

Something else is wrong.

Tony Lawrence
Kerio Preferred Partner and Reseller
Certified for Connect, Control
http://aplawrence.com
freakinvibe

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I have set the delay to 19 seconds and that works perfectly.

Dexion AG - The Blackberry Specialists in Switzerland
https://dexionag.ch
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