S22.Imap System.IO.IOException: The stream could not be read, during client.GetMessages(uids)

Question

I have an application that processes invoices from vendors by using a Gmail inbox and S22.Imap to read emails and pdf attachments. It has been used for several years now without any issue, but lately, I have been seeing "The stream could not be read" errors when trying to get all messages from the inbox to be processed using the command:

IEnumerable<uint> uids = client.Search(SearchCondition.Unseen());   
IEnumerable<MailMessage> messages = client.GetMessages(uids);

This exception seems to only occur when a certain vendor sends a large number of emails at once. I have been looking through the S22.Imap documentation, but have not found anything of help.

Note: I did see this way of getting emails, but the original method I used above is the actual example for "Downloading unseen mail messages" in the documentation:

// Fetch the messages and process each one
foreach (uint uid in uids)
{
     MailMessage message = client.GetMessage(uid);
     ProcessMessage(message);
}

My problem here is that I have not been able to reproduce the exception locally, and I don't really understand how it relates to the client.GetMessages(uids) command.

Is there a maximum number of messages that can be processed this way, or is there a better way to read and process emails?

If client.GetMessages(uids) is the best way to get those emails, is there a good way that I could catch this exception and continue when it does happen?

I would appreciate any advice. Thanks,

Answer 1

Not sure if this will ever even help anyone since it is so particular to this one situation with how we are using s22 to process emails, but I figured I would post the answer anyhow.

The main issue that was happening was that all the emails were being marked 'unread' when using the client.GetMessages(uids) syntax. This marked all emails in the inbox as 'read' (which I counted unread emails to make sure that every email was processed). Changing this method to go through the collected uid one per time prevented this problem. The error still happens once in a while, but it does not mess anything up for the user. The message that failed to get processed just gets processed the next time the app runs. So basically, I just changed how I retrieved the unread emails with S22.Imap and dealt with the errors by catching them and moving on.

//get the message one at a time from uids. catching any rare errors with a message
try
{
    MailMessage message = client.GetMessage(uid);
    ProcessMessage(message);
}
catch(Exception e)
{
    System.Threading.Thread.Sleep(1000);
    SendErrorEmail("An exception has been caught: " + e.ToString() + 
                    Environment.NewLine + "UID: " + uid.ToString());
}