Windows 7 64-bit, Office 2010, Outlook 2010, no Exchange, IMAP incoming, SMTP outgoing (cox.net), 1 small PST file for the IMAP/SMTP account, plus 2 large PST files (2GB and 5 GB) for offline storage.

I recently transitioned from Thunderbird (a couple of days ago).  Everything went OK until I started replying to emails (which means, almost immediately).  Most replies failed to send, getting the "None of your e-mail accounts could send to this recipient" NDR immediately after each attempt.  Normally that's an indicator of a bad "E-mail type" such as mailto, or blank.  In this case, when I check the properties for the email address, the E-mail type shows as blank.  Got it.  When I change the E-mail type to SMTP, the email sends perfectly.

Of course, I have thousands of emails in my storage that I might want to reply to, and spot checking seems to indicate that most have an E-mail type that's blank.  I don't look forward to scrolling through thousands of email address fixing them one by one.  I suppose I'm marginally interested in why this happened, but at this point I'm much more interested in how to fix it.  Is there a setting somewhere that lets me tell Outlook, YES ALL MY OUTGOING E-MAIL TYPES ARE SMTP.  Is there a file I can edit?  Anything?  Please?  Help?

BTW, I already did File | Options | Mail | Send Messages | Empty Auto-Complete List.  I did not, however, try to find the hidden NDK file and try to delete it.  (I've only been using the account under Outlook for a couple of days, and the problem happened with the very first message.)  Oh, another tidbit, when I created the account and sent the obligatory test message, the test message went out and came back in just fine.  And just to confirm: Once I set an email address to SMTP, it works fine after that.

Help?

Thanks!

I forgot to mention ... My Office and Outlook are 64 bit as well.

Hi,

Obviously you have found the reason why the issue occurs: The blank E-mail type.

There are also similar issues in the two threads below:

http://community.office365.com/en-us/f/158/t/62359.aspx

https://social.technet.microsoft.com/Forums/exchange/en-US/ebb37de3-2668-4e39-a419-7c78b10dbcf4/none-of-your-email-accounts-could-send-to-this-recipient

But I have to admit that I haven't found a method to add "smtp" for multiple emails in Outlook, you can try to add "smtp" to some of these address properties, then save them as contacts, check if this can be any help.

Actually in my Outlook IMAP account, there is no such issue, so I'm not sure if this is Thunderbird specific.

I also saw a thread saying some add-ins may change the E-mail type property, you can try to create a new Outlook profile from Control Panel -> Programs and Features, then start Outlook in Safe Mode, add the account in the new profile, check if the issue persists.

To start Outlook in Safe Mode, press Win + R, type "outlook.exe /safe" in the blank box.

If there is no such issue in Safe Mode, consider to disable the suspicious add-ins in Outlook to verify which one caused the problem.

Regards,

Melon Chen
TechNet Community Su

I haven't added any add-ins myself.  Although I just checked and I guess Microsoft adds a bunch of add-ins as part of the installation.  Who knew? 

By the way, I *can* edit the Thunderbird files that got converted over.  Is there a specific line or variable in the normally-hidden part of the header that Outlook is looking for?  That Outlook takes this SMTP information from?