Reply to not correctly recognising sender in Outlook 2010


I have a PC running Windows 7 with Office 2010 SP1. I connected a POP3 account to it and imported contacts into it from Windows Mail as contact cards.

However replying to some emails doesn't work. Probably about 1 in 5 of them. I can't seem to find anything unique about the email addresses it wont reply to.

As an example Karen ( has sent an email when I click reply it passes Karen into the reply to field however it doesn't validate as an email address so when you try to click Send it it doesn't recognise 'Karen' as a valid email address. Yet other email addresses work absolutely fine when I reply to them.

If I add Karen as a contact (Karen a s a display name) and her correct email address it will work as the Check Names function finds the correct info for 'Karen'

Any ideas what could be causing this. This is happening on at least 10+ unique email addresses from different domains so it's not a problem with the email address I'm sending to.

Seems to be something within Outlook causing this.

Thanks for any help in advance.

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Glen KnightCommented:
Can you check the property of the contact for one you are having problems with? Anything untoward? For example a stray < or '
itmtsnAuthor Commented:
Nothing untoward that I can see in any of the email addresses that are failing.

I get a valid email from a valid email address, hit reply and it inserts the display name as the email address which it then can't send to as it's not an existing contact and isn't a correct e-mail address.

I might try recreating the profile from scratch.
Madan SharmaConsultantCommented:
Open your outlook vis run by typing this:-

Outlook.exe /CleanAutoCompleteCache

and check if you are still having this issue.

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Here I agree with "akicute555"

However, if you have alot of email addresses already in the autoComplete Cache....And it sounds like you  know exactly which ones have the issue

I would just delete the individual ones you are seeing the issue with

This can be done by starting to type in their email address
When it shows up as a suggestion
On the right you should see an X
You can click on the X to delete
Or once highlighted, you can press delete on keyboard

Advantage of doing this way, is you will not loose all your AutoComplete email addresses that you didnt have any issues with.

itmtsnAuthor Commented:
This seems to have fixed it. Thanks.

This was a new install of Outlook 2010 so the auto complete was quite small. Also to point out this wasn't happening on existing contacts but on completely new correspondence. i.e Fred Bloggs ( would email you and when you clicked reply all that went into the To: box was 'Fred Bloggs' and when you clicked send it would state 'Fred Bloggs' isn't a valid e-mail address.

I'm not sure why clearing the AutoCompleteCache has fixed this but it doesn't seem to be happening anymore and all email addresses resolve correctly.

Thanks for any help/suggestions on this.
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