This can be one of two things first what anti virus or security system are you running? Second do you have rules set limiting file attachments? If you have imported a security policy there is a good chance you brought this over. By default, Exchange 2007 OWA will let you send attachments of up to 30 MB in size. Depending on your situation, you might want to either increase or decrease this number as we have a mechanism by which you can change the default upload limits of file attachments in OWA. For example: in order to send attachments which are 50 MB or larger: 1. You need to set the MaxRequestLength in web.config to a value larger than 50 MB. The MaxRequestLength in web.config is an ASP.NET setting that prevents requests larger than a certain length which was added to prevent DOS attacks. It is set to 30 MB by default and needs to be increased in order to send attachments larger than 30 MB. This could also be decreased to enforce a lower limit. 2. You need to increase the MaxSubmitMessageSize which is a readonly Mailbox property (MaxSubmitMessageSize = 0x666D0003) and this is where we are getting the 10 MB limit from. This is read from the following places: 1. First read from Mailbox object of the user itself 2. if not found as denoted by "unlimited", Transport Settings Container 3. if not found as denoted by "unlimited", from Org Container (default read from Org Container) In order to set the value, use the following tasks in the Exchange Management Shell: 1. set-transportconfig and then set MaxSendSize (this is in KBs) to 51200 for 50 MB attachments. This will set it for all users Or 2. set-mailbox and set the MaxSendSize (this is in KBs) to 51200 for 50 MB attachments for a specific set of users. Once you set either, you need to recycle store or not access the mailbox for about 15-20 minutes (to let store cache expire) in order for the size change to have affect. Also, the property is stored in AD and subject to replication delays. One more thing that you need to be aware of (sorry, the list just goes on): We have a Request timeout of 60 minutes for any attachment upload request or attachment download (in OWA Basic and Premium). So, if you are trying to upload a 50MB attachment over a 56Kbps link, you will time out and get a HttpWebException (e.g., the max upload is about 25 MB over a 56 Kbps link). So, to summarize, there are two keys to send a large attachment: 1. Modify ASP.NET web.config settings. 2. Modify the MaxSendSize using either the set-TransportConfig (for all users) or Set-Mailbox for individual users. And you need to 3. Make sure the total upload time will be less than 60 minutes (based on your size and the speed of your network link) The web.config change is immediate but the MaxSendSize change takes time, due to caching policy (Mailbox cache, DSAccess delays, and replication delays). Examples: Web.Config change By default, web.config under OWA Vdir (MicrosoftExchange ServerClientAccessOwa) will have the following entry (by default, the max request size is approximately 30MB): <system.web> <httpRuntime maxRequestLength="30000" /> .... </system.web> Change <httpRuntime maxRequestLength="30000" /> to <httpRuntime maxRequestLength="X" /> where X is the desired value in KBs. So, for 50MB, X will be approximately 50000. Change per-user message size limit Go to Exchange Management Shell, and type the following command: Set-mailbox -id:"username" -MaxSendSize:50000 Where "username" is the mailbox identity. This will set the maximum message send limit to approximately 50 MB. You will need to restart store to see the effect immediately. Change all-user message size limit Go to Exchange Management Shell, and type the following command: Set-transportconfig -MaxSendSize: 50000 This will set the maximum message send limit to approximately 50 MB. You will need to restart store to see the effect immediately. - Raj Mukherjee

This can be one of two things first what anti virus or security system are you running? Second do you have rules set limiting file attachments? If you have imported a security policy there is a good chance you brought this over. By default, Exchange 2007 OWA will let you send attachments of up to 30 MB in size. Depending on your situation, you might want to either increase or decrease this number as we have a mechanism by which you can change the default upload limits of file attachments in OWA. For example: in order to send attachments which are 50 MB or larger: 1. You need to set the MaxRequestLength in web.config to a value larger than 50 MB. The MaxRequestLength in web.config is an ASP.NET setting that prevents requests larger than a certain length which was added to prevent DOS attacks. It is set to 30 MB by default and needs to be increased in order to send attachments larger than 30 MB. This could also be decreased to enforce a lower limit. 2. You need to increase the MaxSubmitMessageSize which is a readonly Mailbox property (MaxSubmitMessageSize = 0x666D0003) and this is where we are getting the 10 MB limit from. This is read from the following places: 1. First read from Mailbox object of the user itself 2. if not found as denoted by "unlimited", Transport Settings Container 3. if not found as denoted by "unlimited", from Org Container (default read from Org Container) In order to set the value, use the following tasks in the Exchange Management Shell: 1. set-transportconfig and then set MaxSendSize (this is in KBs) to 51200 for 50 MB attachments. This will set it for all users Or 2. set-mailbox and set the MaxSendSize (this is in KBs) to 51200 for 50 MB attachments for a specific set of users. Once you set either, you need to recycle store or not access the mailbox for about 15-20 minutes (to let store cache expire) in order for the size change to have affect. Also, the property is stored in AD and subject to replication delays. One more thing that you need to be aware of (sorry, the list just goes on): We have a Request timeout of 60 minutes for any attachment upload request or attachment download (in OWA Basic and Premium). So, if you are trying to upload a 50MB attachment over a 56Kbps link, you will time out and get a HttpWebException (e.g., the max upload is about 25 MB over a 56 Kbps link). So, to summarize, there are two keys to send a large attachment: 1. Modify ASP.NET web.config settings. 2. Modify the MaxSendSize using either the set-TransportConfig (for all users) or Set-Mailbox for individual users. And you need to 3. Make sure the total upload time will be less than 60 minutes (based on your size and the speed of your network link) The web.config change is immediate but the MaxSendSize change takes time, due to caching policy (Mailbox cache, DSAccess delays, and replication delays). Examples: Web.Config change By default, web.config under OWA Vdir (MicrosoftExchange ServerClientAccessOwa) will have the following entry (by default, the max request size is approximately 30MB): <system.web> <httpRuntime maxRequestLength="30000" /> .... </system.web> Change <httpRuntime maxRequestLength="30000" /> to <httpRuntime maxRequestLength="X" /> where X is the desired value in KBs. So, for 50MB, X will be approximately 50000. Change per-user message size limit Go to Exchange Management Shell, and type the following command: Set-mailbox -id:"username" -MaxSendSize:50000 Where "username" is the mailbox identity. This will set the maximum message send limit to approximately 50 MB. You will need to restart store to see the effect immediately. Change all-user message size limit Go to Exchange Management Shell, and type the following command: Set-transportconfig -MaxSendSize: 50000 This will set the maximum message send limit to approximately 50 MB. You will need to restart store to see the effect immediately. - Raj Mukherjee