Hello, me again with another issue.... :), Exchange 2003 SP2, SBS 2003 Users are reporting that they have emailed a specific domain and the email is in Sent Items. Other party never receives it. No NDR is ever generated. I rebooted the server tonight for an unrelated patch and a batch of NDRs were delivered to various mailboxes relating to email sent some days or weeks ago. I have googled this and it appears to be a known issue related to greylisting, but would welcome some confirmation or explanation about what to do. Many thanks.

Old issue, messages likely got stuck in the temp table. When server gets rebooted the messages in the temp table get reprocessed. There are many reasons why messages can get stuck, sometimes AV or other third party apps. I would also make sure your Exchange server is up to date with latest roll ups as well as generic windows patches and any updates for your third party apps. Have You Checked Your SMTP Mailbox Temporary Tables Lately? http://www.windowsitpro.com/article/smtp/have-you-checked-your-smtp-mailbox-temporary-tables-lately-.aspxJames Chong MCITP | EA | EMA; MCSE | M+, S+ Security+, Project+, ITIL msexchangetips.blogspot.com