exchange FindFolders: specific value has invalid HTTP Header Characters

ReMED Services Orders 0

Hi, I recently started hitting a bug, and any suggestions on how to work around this would be greatly appreciated.

There were no changes to the code in the past 12 months+, and suddenly the application is breaking at this line:

var ewsClient = new ExchangeService();
ewsClient.Url = new Uri("https://outlook.office365.com/EWS/Exchange.asmx");
ewsClient.Credentials = new OAuthCredentials(authResult.AccessToken);
ewsClient.ImpersonatedUserId =
new ImpersonatedUserId(ConnectingIdType.SmtpAddress, mailbox);

//Include x-anchormailbox header
ewsClient.HttpHeaders.Add("X-AnchorMailbox", mailbox);

var folders = ewsClient.FindFolders(WellKnownFolderName.Inbox, new FolderView(10));

This last line throws an error:

Specified value has invalid HTTP Header characters.
Parameter name: name

Thank you!

Miguel Gonçalves | AVANADE 886 Reputation points

2024-06-11T23:00:22.38+00:00

Hi ReMED,

"Specified value has invalid HTTP Header characters", indicates that there’s an issue with the HTTP header you’re setting.

Although you mentioned no recent code changes, consider any external factors that might affect the request. For example, was there a new subfolder created in the Inbox recently?

Investigate whether any changes in the environment (such as server updates or configuration adjustments) could be causing this issue.

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exchange FindFolders: specific value has invalid HTTP Header Characters