Text entry speed does not help me ... have waited up to 30 secs between entries. Seems to recognise addresses but auto complete insists on marking text to red regardless of entry speed.

Thanks for responding anyways.

I think the issue is corrupt files.

open your profile directory and have a look at what .MAB files are in that directory

abook.mab is your personal address book. History.mab is your collected addresses. I suggest moving both of them to another directory with Thunderbird closed and then restarting Thunderbird. Might be that will fix both issues.

Have tried to eliminate possibility of corrupt *.mab files by exporting personal address book to another folder as *.ldif, then closed TB, then deleted all *.mab files in profile directory, then restarted TB, then imported the *.ldif into TB as my personal address book. TB recognises addresses but auto complete still insists on marking "To" text to red.

Thanks for responding anyways.

Partial Fix!! The following workaround provides a way to ignore addressbook match:- Go to Edit/Preferences/Advanced/General/Config_Edit Search for 'mail.autoComplete.highlightNonMatches' set it to 'false' This worked for me on Xubuntu.