{"id":491,"date":"2009-05-01T11:08:51","date_gmt":"2009-05-01T11:08:51","guid":{"rendered":"http:\/\/andyparkes.co.uk\/blog\/index.php\/2009\/05\/01\/exchange-2003-greylisting-and-delayed-ndrs\/"},"modified":"2009-05-01T11:08:51","modified_gmt":"2009-05-01T11:08:51","slug":"exchange-2003-greylisting-and-delayed-ndrs","status":"publish","type":"post","link":"https:\/\/andyparkes.co.uk\/blog\/index.php\/2009\/05\/01\/exchange-2003-greylisting-and-delayed-ndrs\/","title":{"rendered":"Exchange 2003 – Greylisting and Delayed NDR’s"},"content":{"rendered":"

Recently I’ve heard from various different clients having problems when sending emails to the NHS<\/a><\/p>\n

The error message usually reads<\/p>\n

\n

<****.com #4.0.0 smtp;451 ******@****.nhs.uk>… Requested mail action not taken: mailbox unavailable<\/strong><\/p>\n<\/blockquote>\n

 <\/p>\n

Due to the message specifically saying \u201cmailbox unavailable\u201d and it\u2019s several different clients all sending to the same organisation I\u2019ve been placing the blame with the NHS<\/p>\n

This morning I found out that assumption was wrong<\/p>\n

I was doing some work on one of our clients servers and needed to restart the SMTP service<\/p>\n

About two minutes later I got a call from the client in question to say they had all suddenly started get a glut of NDR\u2019s<\/p>\n

Initially it looked like they were all for messages sent to the NHS but we found one or two that were to different domains and also spotted that some of these messages were originally sent last week<\/p>\n

It was one of the other emails that made me look into this further. The error in this case was<\/p>\n

\n

<****.com #4.0.0 smtp;450 <<\/strong>****@******.com<\/strong>>: Recipient address rejected: Greylisted for 5 minutes><\/strong><\/p>\n<\/blockquote>\n

 <\/p>\n

Greylisting!<\/strong> <\/p>\n

This is where a mail server temporarily rejects a message when it is first sent. When the mail server retries it will be accepted on the second attempt. The theory is that spammers get so many rejections they don\u2019t try again (more info available at http:\/\/www.greylisting.org\/<\/a> and http:\/\/en.wikipedia.org\/wiki\/Greylisting<\/a>)<\/p>\n

While looking into this previously I’d been told that the NHS were using greylisting as part of their spam prevention measures<\/p>\n

Looking at the two error messages that both use the same SMTP failure code (4.0.0) which indicates a temporarily failure (i.e please try again!)<\/p>\n

The NHS description is less helpful than the other one<\/p>\n

So i still had to figure out what had caused all the NDR\u2019s to suddenly appear<\/p>\n

On the greylisting.org site there is a page called \u201cProblem MTA\u2019s\u201d<\/a>. This a single page with one entry<\/p>\n

 <\/p>\n

\n
<\/h5>\n

Microsoft Exchange 2003 and greylisting<\/h4>\n

There is a bug in MS Exchange 2003 when sending to greylisting servers. Sometimes the server will fail to re-queue messages sent to some servers that implement greylisting. More information:<\/p>\n

groups.google.com\/group\/mi…64d5749ee7cb<\/a><\/p>\n

groups.google.com\/group\/mi…07ac14b116db<\/a><\/p>\n

According to ozinm on our forums there is a possible hotfix available from Microsoft now: www.greylisting.org\/forums\/showthread.php?tid=18<\/a><\/p>\n<\/blockquote>\n

 <\/p>\n

The threads there talked about the exact same problem I had. It also looks like the problem has been around October 2005. It has various workarounds including using a batch file to restart the SMTP service every day!<\/p>\n

Eventually a hotfix mentioned is here: 934709<\/a> <\/p>\n

HOWEVER! This is for servers that are running Windows 2003 with the SMTP service. It doesn\u2019t apply if your using Exchange 2000 \/ 2003<\/p>\n

After a bit more searching I finally found this <\/p>\n

Article ID: 950757 – E-mail senders do not receive an indication that some messages have been held by Exchange Server 2003 until the SMTP service, the Microsoft Exchange Information Store service, or the Exchange server is restarted<\/a><\/p>\n

This fits the problem exactly. I\u2019ve applied to the server I’ve been dealing with today so I’ll keep an eye on it and apply to the other servers that have noticed similar issues<\/p>\n

Another solution would be to use a smart host to deliver your messages for you<\/p>\n

One thing i have learnt here is that I probably should have double checked the SMTP code instead of relying on the error description. I generally only get to the SMTP code if I can\u2019t find a problem using other troubleshooting methods (Exchange messages tracking, telnet tests, etc) <\/p>\n","protected":false},"excerpt":{"rendered":"

Recently I’ve heard from various different clients having problems when sending emails to the NHS The error message usually reads <****.com #4.0.0 smtp;451 ******@****.nhs.uk>… Requested mail action not taken: mailbox unavailable   Due to the message specifically saying \u201cmailbox unavailable\u201d and it\u2019s several different clients all sending to the same organisation I\u2019ve been placing the<\/p>\n

<\/span>Read More<\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[13],"tags":[],"class_list":["post-491","post","type-post","status-publish","format-standard","hentry","category-exchange-2003"],"yoast_head":"\nExchange 2003 – Greylisting and Delayed NDR’s - Andy's Techie Blog<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/andyparkes.co.uk\/blog\/index.php\/2009\/05\/01\/exchange-2003-greylisting-and-delayed-ndrs\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Exchange 2003 – Greylisting and Delayed NDR’s - Andy's Techie Blog\" \/>\n<meta property=\"og:description\" content=\"Recently I’ve heard from various different clients having problems when sending emails to the NHS The error message usually reads <****.com #4.0.0 smtp;451 ******@****.nhs.uk>… Requested mail action not taken: mailbox unavailable   Due to the message specifically saying \u201cmailbox unavailable\u201d and it\u2019s several different clients all sending to the same organisation I\u2019ve been placing theRead More\" \/>\n<meta property=\"og:url\" content=\"https:\/\/andyparkes.co.uk\/blog\/index.php\/2009\/05\/01\/exchange-2003-greylisting-and-delayed-ndrs\/\" \/>\n<meta property=\"og:site_name\" content=\"Andy's Techie Blog\" \/>\n<meta property=\"article:published_time\" content=\"2009-05-01T11:08:51+00:00\" \/>\n<meta name=\"author\" content=\"Andy Parkes\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Andy Parkes\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"3 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\/\/andyparkes.co.uk\/blog\/index.php\/2009\/05\/01\/exchange-2003-greylisting-and-delayed-ndrs\/\",\"url\":\"https:\/\/andyparkes.co.uk\/blog\/index.php\/2009\/05\/01\/exchange-2003-greylisting-and-delayed-ndrs\/\",\"name\":\"Exchange 2003 – Greylisting and Delayed NDR’s - 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