Email Flood - Denial of Service
I have found myself in the following scenario a number of times recently and would like to get some feedback from others. The environment is Exchange 2007 with dedicated HT,CAS and Mailbox Servers. The users are mapi connected Outlook 2007 cached mode. The user would like to email most of the users in the organisation. Therefore, the user constructs 50 seperate emails in outlook and block selects large portions of the GAL which includes mailbox recipients, distribution lists etc. The user also attaches files totaling 6MB to these emails. Each email contains approximatley 40-50 recipients made up of mailboxes and distribution lists. The user then sends all 50 emails. I find that the submission queue begins to backup as the HT servers struggle to process these emails. I find that the MSexchagetransport service consumes all available CPU. The mails are delivered and processed slowly however all mail submitted after the bulk mail is sat in the submission queue. The bulk mails are slowly moved from the submission queue to the delivery queue for the appropriate mailbox server. Exchange applies backpressure (high) but still the issue persists. This process seems to take many hours and causes significant mail backlog. The question is how can I prevent this from happening? I know there is a maxrecipientsenvelope that I can specify - but I'm not sure this will help. Any thoughts?
May 17th, 2010 8:26pm

Hi, Can you block this user via firewall policy? Is is a DOS or DDOS? MiguelMiguel Fra / Falcon ITS Computer & Network Support, Miami, FL Visit our Knowledgebase Sharepoint Site
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May 18th, 2010 5:35am

Unfortnatley this is a genuine user who is not particaulary computer literate. The other worry I have is that any of the users could do something similiar - are there are precautions I can put in place?
May 18th, 2010 10:14am

Sounds like you are in a difficult predicament. If you place restrictions, you are denying him/her legitimate use of technology (large attachments, multiple users) on the other hand if you don't, it can get out of hand. Maybe you can explain why their actions are causing technological mayhem and have them take an adult-oriented, self disciplined approach. Unless of course you are an IT manager for K-6 ;-) CheersMiguel Fra / Falcon ITS Computer & Network Support, Miami, FL Visit our Knowledgebase Sharepoint Site
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May 20th, 2010 6:49am

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