I get OnImapProtocolException() when trying to read email using MailKit

Question

I am using MailKit v. 4.4.0 to read emails from an IMAP Server. My code is as follows:

DateTime deliveredAfterDate = ... some date value
using (var client = new ImapClient())
{
  client.Connect(_emailConfig.ImapServer, _emailConfig.ImapPort, true);
  client.Authenticate(_emailConfig.UserName, _emailConfig.Password);

  var inbox = client.Inbox;
  inbox.Open(FolderAccess.ReadOnly);

  var query = SearchQuery.DeliveredAfter(deliveredAfterDate);
  IList<UniqueId> emailIds = inbox.Search(query);
    
  foreach (var uid in emailIds)
  {    
      // Exception is thrown HERE
      var message = inbox.GetMessage(uid); // <-- HERE                               
      if (message == null)
      {
          continue;
      }

      // Save email in DB
      IncomingMail newMail = new IncomingMail()
      {
          MessageId = message.MessageId,
          Subject = message.Subject ?? string.Empty,
          FromName = message.From.Mailboxes.FirstOrDefault()?.Name ?? string.Empty,
          FromAddress = message.From.Mailboxes.FirstOrDefault()?.Address ?? string.Empty,
          Timestamp = message.Date.LocalDateTime, // .DateTime,
          TextBody = message.TextBody ?? string.Empty,
      };
      await repo.InsertMailAsync(newMail)
  }

  client.Disconnect(true);
}

The above code is executed inside a worker service. Once the operation is completed the whole process is repeated after one minute.

It works most of the times. Emails are properly read and saved in my DB. However periodically I get the following exception:

Exception generated. Caller Member Name: Read, Caller Path: D:\eDirectorate\source\eProtocol\eProtocol.Service\Services\EmailReader.cs, Caller Line Number: 146 11:50:27 ERROR Exception stack trace: at MailKit.Net.Imap.ImapEngine.OnImapProtocolException() at MailKit.Net.Imap.ImapEngine.Iterate() at MailKit.Net.Imap.ImapFolder.GetMessage(UniqueId uid, CancellationToken cancellationToken, ITransferProgress progress) at eProtocol.Service.Services.EmailReader.Read() in D:\eDirectorate\source\eProtocol\eProtocol.Service\Services\EmailReader.cs:line 88

11:50:27 ERROR FETCH failed: Internal error occurred. Refer to server log for more information. [2024-03-15 11:50:27]

Any idea why this exception occurs?

Answer 1

1. I suggest to handle the exception first by surrounding your code by

   try{}
   catch(Exception ex)
   {
       // Handle other exceptions
       Console.WriteLine("An error occurred: " + ex.Message);
   }
   

2. Server-side issue: There might be an issue with the IMAP server itself, such as resource constraints, network issues, or software bugs. This could be temporary and may resolve itself over time.