Sunday, March 25, 2007

Exchange 2003 Outlook Mobile Access 1801 error

OK, There is absolutely almost no answer on the web for the MSExchangeOMA 1801 error. That’s because stock users of Exchange and IIS won’t have the issue that I had.

The very short answer: WebDav defaults to checking for stuff via IIS http on port 80.

If your IIS has another HTTP (not SSL/HTTPS) port as all it’s listening on, OMA/Outlook Mobile Access will not work. Make sure port 80 is listened to by IIS.

Why I had Internet Information Server on another port:

It was a legacy issue. I had OWA/Outlook Web Access through a firewall on a non-standard port. OWA does NOT like firewall port not matching IIS port. So HTTP port on IIS was chosen to match the firewall port for IIS for NON-SSL traffic. Later, I didn’t need non-SSL traffic for OWA and didn’t bother to change the IIS port. When OMA came up with

Unable to connect to your mailbox on server Servername. Please try again later. If the problem persists contact your administrator.

It was because it was attempting to contact internally via WebDAV on WebDAV’s default connection: http://Servername:80/Exchange/mailbox

the :80 (hidden, but the default port for web) was not accessible because my default http port on IIS wasn’t listening on port 80. This caused the same error from outside my firewall all the way to trying the OMA connection at localhost on my exchange server.

Thanks to

for knocking me in the head about things I didn’t realize I hadn’t done.


Anonymous said...

Thank you SOOOO much for your post. I've been looking for a solution to error 1801 all day and couldn't figure it out.

Of course it makes sense when you describe it that way. Too bad you can't tell WebDAV to look on another port.

tech guy said...

You're welcome. I realize this is an obscure error, with specific reasons, but your comment makes it worth the effort to log the issue.

Unknown said...

OOOh i have to agree, been fighting with this for quite some time now.

Just adding port 80 as well worked wonders, now i can sync all my stuff at home again.

Funny that MS error codes arent coming with a bit more hint :)


Unknown said...

Aaah nice, this problem has been bugging me for quite some time.

Was fairly certain it was because i had moved the http port to a different port. But webmail works just fine.

Now i can sync my Phone and my PDA again.

Thx alot!


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