yogi_Create One Composite Unique And Sorted List From Two Email Lists In Different Sheets

Yogi Anand, D.Eng, P.E.                                         Google Spreadsheet                            www.energyefficientbuild.com
user vanarkel said:
Check if a value is unique in columns of multiple sheets (removing duplicate email addresses)
I have spreadsheet which I use to administrate my members. This spreadsheet contains multiple member categories, for each member category I have a separate sheet in which I edit them. I want to keep these categories in different sheets, because editing everything from a single sheet will become to messy.In each sheets there is one column called email, now I want to know if the email addresses are duplicated in this sheet or in other sheets. 

What is the easiest way to do this automatically. 

I really hope someone can help me :) Thanks a lot in advance!!!!

Pss: I can copy all email addresses to one new sheet in column A, then insert the function =unique(A:A) in B1 and then compare these columns. In that way I know which email addresses are duplicated. But the problem is then that I have to manually copy new email address in this list each time I edit a seperate sheet.

Ps: I searched everywhere, but I couldn't find an answer hopefully somebody can help me
And

finally vanarkel said:

If someone can tell me how to do something like this: =sort(Sheet1!D:D;Sheet2'!D:D) so that I could sort the values from 2 different columns in one column I would be really helped a lot too!!

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following is solution to the problem ... where I have combined Email lists from two different sheets into one combined sorted and unique list