Question on behavior of MailMessage Load(System.IO.Stream stream)

Aspose.Email Product Family
1

Hi,

I am experiencing a strange behavior in my application, so I am trying to troubleshoot if Aspose.Email for .NET (25.2.0) could somehow be the culprit.

I load an eml email file as a byte array from disk:

rawData = File.ReadAllBytes(filePath);

After that I parse the message using MailMessage.Load():

public MailMessage TryLoadMessage(byte[] emailBytes)
{
    try
    {
        MailMessage message;
        using (var ms = new MemoryStream(emailBytes))
        {
            message = MailMessage.Load(ms);
        }
        // read out some properties like Subject, From, Body, etc.
        return message;
    }
    catch (Exception ex)
    {
        _logger.LogError("Could not parse the email message.", ex);
    }
    return null;
}

Later on, I pass the same rawData byte array (the original one, not a copy) to be saved to a database (varbinary(max) column).

Issue

On rare occasions, the byte array that gets saved to the database appears to have been modified - specifically, headers are being reformatted. The X-Authority-Analysis header and some Content-* headers get split into multiple lines with continuation (folding), and their order in the file changes.

Examples

Original file on disk:

Content-Type: application/pkcs7-mime; smime-type=enveloped-data; name="smime.p7m"
Content-Disposition: attachment; filename="smime.p7m"
Content-Transfer-Encoding: base64
MIME-Version: 1.0
X-Authority-Analysis: v=2.4 cv=f8tFxeyM c=1 sm=1 tr=0 ts=68dd30e5 cx=c_pps a=ozr7GCmQR6vTER9hNFG0XQ==:117 a=ozr7GCmQR6vTER9hNFG0XQ==:17 a=z/mQ4Ysz8XfWz/Q5cLBRGdckG28=:19 a=lCpzRmAYbLLaTzLvsPZ7Mbvzbb8=:19 a=Ol13hO9ccFRV9qXi2t6ftBPywas=:19 a=xqWC_Br6kY4A:10 a=x6icFKpwvdMA:10 a=beYOY05SAfMA:10 a=6x1IRoMcAqDwjAA7qosA:9 a=ZVk8-NSrHBgA:10 a=Y2PKsZ1wOLwA:10 a=kppHIGQHXtZhPLBrNlmB:22

File stored in database (note headers reordered and X-Authority-Analysis split into multiple lines):

MIME-Version: 1.0
X-Authority-Analysis: v=2.4 cv=f8tFxeyM c=1 sm=1 tr=0 ts=68dd30e5 cx=c_pps
 a=ozr7GCmQR6vTER9hNFG0XQ==:117 a=ozr7GCmQR6vTER9hNFG0XQ==:17
 a=z/mQ4Ysz8XfWz/Q5cLBRGdckG28=:19 a=lCpzRmAYbLLaTzLvsPZ7Mbvzbb8=:19
 a=Ol13hO9ccFRV9qXi2t6ftBPywas=:19 a=xqWC_Br6kY4A:10 a=x6icFKpwvdMA:10
 a=beYOY05SAfMA:10 a=6x1IRoMcAqDwjAA7qosA:9 a=ZVk8-NSrHBgA:10
 a=Y2PKsZ1wOLwA:10 a=kppHIGQHXtZhPLBrNlmB:22
[... other headers ...]
Content-Type: application/pkcs7-mime; smime-type="enveloped-data"; name="smime.p7m"
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename="smime.p7m"

My Question

Can MailMessage.Load() modify the underlying MemoryStream or the byte array that was used to create it? I’m using the default new MemoryStream(emailBytes) constructor which I guess creates a writable stream backed by the byte array. Could Aspose.Email be writing back to this stream during parsing (e.g., normalizing headers, reformatting, etc.)?

Additional Context

  • This happens intermittently in production and cannot be reproduced in test environments
  • The same rawData byte array reference is used for both parsing and database storage
  • .NET Framework 4.8
  • No other code touches the byte array between File.ReadAllBytes() and database storage besides the TryLoadMessage() call

Possible workarounds I’m considering

  1. Create a read-only MemoryStream: new MemoryStream(emailBytes, writable: false)
  2. Clone the byte array before parsing: var copy = (byte[])emailBytes.Clone()

Would appreciate your guidance on whether Aspose.Email could be modifying the stream/array, and if so, what the recommended approach is to prevent this.

Thank you!

2

@dimitrovski

The behavior you’re experiencing with MailMessage.Load() modifying the underlying MemoryStream or byte array is a valid concern. When you create a MemoryStream using the constructor new MemoryStream(emailBytes), it creates a writable stream that is backed by the original byte array. This means that any modifications made to the stream can affect the original byte array.

In your case, MailMessage.Load() may be normalizing headers or reformatting them, which could lead to the changes you’re observing when saving the byte array to the database.

To prevent this issue, consider the following workarounds:

  1. Create a Read-Only MemoryStream: You can create a read-only MemoryStream by using the constructor new MemoryStream(emailBytes, writable: false). This will ensure that the original byte array cannot be modified during the loading process.

    using (var ms = new MemoryStream(emailBytes, writable: false))
{
    message = MailMessage.Load(ms);
}

  2. Clone the Byte Array: Another approach is to clone the byte array before parsing it. This way, you ensure that the original byte array remains unchanged.

    var copy = (byte[])emailBytes.Clone();
using (var ms = new MemoryStream(copy))
{
    message = MailMessage.Load(ms);
}

Both of these methods will help you avoid any unintended modifications to the original byte array when loading the email message.

If you continue to experience issues, consider logging the state of the byte array before and after the Load() call to further diagnose the problem.

3

Is there perhaps a chance for somebody other then the AI to write something here?

I think it’s a very simple question. I know this is the “free forums” but I (my organization) is still a paying customer.

Thanks

4

Hello @dimitrovski,

Thank you for the detailed description.
Normally, MailMessage.Load() reads data without modifying the original stream. However, it is worth checking this to rule out any side effects.

Have you tried reproducing the issue in a test environment using the same email that caused it in production?

You can make the MemoryStream read-only ( new MemoryStream(emailBytes, writable: false)) to ensure that no modifications are possible. If any write operation is attempted, an exception will be thrown, which will confirm whether any write operations occur during loading.