I recently installed Outlook 2003 on two Windows XP systems and use an online exchange server. I am receiving the same error message on both systems. The error states that "The messaging interface has returned an unknown error. If the problem persists, restart Outlook." I restart Outlook, but no luck. It occurs in at least 5 scenarios: 1) printing anything in Outlook; 2) trying to save and close a new appointment in calendar; (3) trying to invite attendees in calendar; (4) trying to create a new task;(5) trying to save a new contact. I did some online research and see that this is a problem for many people. Please help

Did you try repairing the pst file using the repair tool and or checking the add-ins listed in the advanced options under add-in manager?

Thanks. This was one part of the problem. The other was a bad profile. I contacted the online exchange hosting company and we recreated the profile.

Thanks for the advice. Made me think what i had done previous to getting the error. I had set up a "personal address book" ontop of my outlook address book then removed it. After i removed it i started getting this error. I just added it back in again and now i can reply to all. Thanks Gary

i installed outlook 2003 but i am not able to send mails an error message pops out reading "The messaging interface has returned an unknown error restart Outlook."Please help

I had this problem and solved it by deleting the outlook profile in...C:\Documents and Settings\MrJealousy\Local Settings\Application Data\Microsoft\Outlook\it recreates it when you restart outlook.This didn't work for me on its own, although I have seen posts where it supposedly has.So, on my pc I had Office 2003 complete install and Access 2000 (dont ask why!) and decided to uninstall Access 2000.Then I did a registry clean using regseeker and fired up Outlook and it sends and replies to emails now.Hope this helps.

I've also seen a post say that this works... On the Start menu Click File -> Run And then paste in the line Regsvr32.exe %Windir%\System32\Ole32.dll And then click okay. ...but it didn't work for me!

I was searching for this for about 2 weeks. Thanx a lot. This also solved my adobe pdf previwerproblem.

I've successfully resolved this error by simply creating a new Outlook profile. My symptoms were before: "The messaging interface has returned an unknown error". Outlook version was 2003 SP2 running in an Exchange environment. I couldn't open a new mail/contact or even press Reply/Forward etc. Outlook reinstall didn't help. However creating a new Outlook profile worked like a charm.

This is happening in my environment also. we are using MM Mail version 7.2.568.8. (Modular Messaging Mail from Avaya). I think that different scenarios are causing this problem. A big one is when the user doesn't wait for a message to finish and close before opening the next voice mail message that is in their Inbox. When this issue is brough to attention then the following is the work around:Teach the user to open TAsk Manager and cancel the Voiceform.exe and then continue. I found that some users closing Outlook, not waiting until the Outlook.exe was closed, then reopening and the problem was worse. Then they reboot. So many reboots in a day is bad for productivity.After troubleshooting I seem to have only one user who keeps me notified and I will try the profile recreating solution. The other users say they have no further problems after I followed up.

The solution from ziegel worked for me.

The solution from MrJealousy did not work for me.

I bet it must have resolved after creating new profile?Arun Kumar | MCSE - 2K3 + Messaging | ITIL-F V3

ziegel's solution worked for me.detailed instructions here: http://outlook-tips.net/howto/profile.htmthanks!

Ziegel's new profile solution worked for methanks!

It just worked for me! My problem was out of the blue it started popping out this error when trying to send an attachment. I uninstalled/restarted/reinstalled, ran scanpst, outlook.exe /cleanprofile to no avail. I can't afford creting a new profile. But Regsvr32.exe %Windir%\System32\Ole32.dll did the trick, thanks a lot! My system is a ThinkPad W510 with W7 Ultimate with MSO2007, 16GB RAM, 500GB HD, MX920. Cheers, Ost

The error "The messaging interface has returned an unknown error" is back again today when I tried to send an attachment. I tried Regsvr32.exe C:\Windows\System32\Ole32.dll again but at this time it didn't work... :-(... Any ideas? Thanks, Ost

I had this same isue and resolved by recreating Outlook profile. Thanks for the advice!