I have enabled incoming email in a large multi-web application farm. I have it working a number of places, but it will not work for one particular web application. I see the email land in the /drop folder. If I remove the email address from the library in http://nonworkingapp web application and use it on a library in a http://working web application, then the email is processed successfully. Conversely, if I take an address from a library in http://working and move it to a library in http://nonworkingapp it does not work. I've tried multiple site collections on http://nonworkingapp. This rules out any SMTP issues, etc. and means the issue is bound to this web application. Permissions are the same between the "non-working" and "working" locations: domain users are members on the site, and the library inherits permissions from the site.
The error in the ULS log is the typical error processing message, but it gives no additional information.
The Incoming E-Mail service has completed a batch. The elapsed time was 00:00: 00.0156294. The service processed 2 message(s) in total. Errors occurred processing 2 message(s): Message ID: Message ID:
Typically, you see "alias not found" or some permissions or quota issue here, but this issue is NOT the same as those. In this case NO additional information is provided, even with Verbose logging on.
Edit: running stsadm.exe -o refreshdms -url http://one/failing/site fixed some similar issues where "Unknown alias" was reported even though the list did have an alias (see here: http://blogs.technet.com/b/vinitt/archive/2009/07/15/e-mail-enabled-list-alias-information-is-not-synchronized-between-configuration-database-and-content-database.aspx). This did not fix the issue for the case mentioned above.
What could possibly be the issue preventing incoming email from working on this one web application?