example:
Today(13-07-2017 or 13th July) I want to write a mail to XYZ to inform that i will be out of office.

i write as below,

Hello XYZ,

I will be out of office on 16th June due to some personal reasons.
Thanks for Understanding.
Regards,

Now in the above mail 16th June is out-of-date,but the sender is unaware of this.

Action outlook can take:
look for the mail subject: leave request/out of office / absence etc
and the date in mail is outdated

solution: Outlook can pop-up a message to the sender saying you have a out-of-date in your mail, do you still like to send this message?

This would likely be categorized as a quick access feature.

Having the ability to perform general tasks while using the least amount of time would be the greatest enhancements anything can get.
The ability to find and group quickly specific keywords, terms, numbers, letters, names, dates, sizes, and just in general all related emails very quickly in the real world of business and personal matters outweighs the need for more functions since if we work faster we progress faster we accomplish more faster and ultimately everything else will come into play "Quickly" after that.
I would say the fact we are still using and needing the "Column Tabs" at all is just silly.
I can easily see a much more efficient method which actually eliminates these things entirely and increases the space available for other useful aspects to be added. The way I would say this can easily be done is. For example lets say your going through emails and trying to find a bunch or related work orders, case emails, financial documents, etc.. you would generally do it in this order or fashion. (Lightbulb goes off > think of how to find the relative info > oh yea, Search feature > or better yet wait, lets sort by date or name attributes > and so you move the mouse over option > Click the option > and begin typing or using the "cached attributes" > you then begin sorting through them and like that you have your emails or even documents in excel this could apply)

HOWEVER....

Lets try a new approach.... "Lightbulb" You know what to look for (In fact you can see a few of the instances already in recent emails) > SO now what you do is you simply either hold a key or click down to either begin a series of a key shortcut, or just press a key combo putting you in super search mode or rather a more fitting name "Spark Search" as I would call it > next when you click on any part of email whether it be a few letters, a few words, or even a few attachments (The list goes on and on) it will automatically pull and group these items based on specific user preferences or even using an AI based approach to allow the users experience to go off the charts since all of the info and emails and names and numbers are instantly or even if it can just be as fast as the general search option that would suffice but the info is grouped and organized and shows you exactly what you are in need of. Here are some more easy to understand steps and reasons and practical uses.

You have 100+ emails all with the subject containing the first three letters "INC" for the word incident. You need to find the Incidents which are related to a specific software say Outlook for example. you also need to narrow down more by finding the ones sent by a certain group or even want to include the ones for Outlook, From Matthew, Sent with attachments but, you also figure you need to have the ones with those attributes but you want to compare a few that are ent by matthew for outlook with images sent withing the last year with the ones sent by Microsoft with attachments and regarding outlook, So you would normally need to do many searches, many extra organizing steps, maybe even copy and pasting to MS word or Excel may be involved. INSTEAD you enter this "Eagle Eye AI" mode and begin clicking on the name matthew then a differnt key is pressed and you click on Microsoft then you just start clicking away all the while you get a popup which instanly pulls the emails from matthew, it even pulls up the Microsoft ones and knows to separate them based on previous times its been done and you can see immediately that you are making faster progress because you see that you no longer need to includ the attachments since the info you would have spent all day trying to find is right there, organized, redy to compare, you can click or hover on certain parts to interactively open or close parts of the email, you can color code, group the results etc Its not necessary to have the To From Received Subject Body Priority column label tabs up top which you would click to sort through the list below because you already know that the email your seeing that sent you the msg is the "From" and if you need to find a specific one that you cannot see, click anywhere on the Subject, From, date, Etc etc and just search the first few letters, and then the email addres you forgot about and couldn't see is there as it would be with search feature. You can not start selecting the parts you need to locate and it will just improve the results as you go.

Also the feature will not eliminate classic searching but instead enhance it and move it to where it is not obscuring your view from the important details.

Basically to sum it all up, get rid of the fat and excess cumbersome functions NOT BY REMOVING ENTIRELY, rather just away from being a distracting point. Another key problem with lacking performance speed. If you simplify and superfy the functions to be readily available without obscuring ones view and workspace, then you ultimately made something great that is worth using. Now if you have read this far Bravo, I am appreciative of your time and consideration I could write for days on end to specify improvements. But the best way is to actually simplify the explanation herein but also relay the powerful message to Microsoft which can be the game changer for business and residential use alike.

Enter "Power Search" > click identifiable attributes which are needed to find > Done (Unless you need to go a few steps further)

Another key part to improve upon is the Color schemes. They are really washed out and hard to stare at. I would add the full color spectrum customizations that allows every inch of the client, words, menus, tabs, backgrounds, borders, shadows etc etc to be changed to the liking of the user. THE ONLY ISSUE, would be making it too complicated by allowing too many areas to be done individually. If you change one part, allow the option to continue with the related areas to be auto colored with that color or allow to select the areas by clicking. kind of like Paints paint bucket tool but while looking at the GUI you select parts to color and rearrange etc. CUSTOM is key, but too hard to customize as I see In so many cases makes it worse than simple and plain. two words SIMPLE POWERFUL. and of course advanced is an option that you always would want to allow the savvy ppl to use.

Finally, Allow the ability to scroll while holding another key down to change through recent settings and configurations set in office products and see the commonly used views first in the scroll. Just make things Fast, Easy, Advanced, Customizable, Powerful, and Stable. Great job so far. wish I coud find specific pieces of specific emails from specific people in or around specific dates and within specific folders and the ability to color code my folders and the emails alike to quickly see them in searches etc.

The idea is: "Microsoft Improvements" should be improvements. So what worked well in the past is built upon. Not destroy what was working well, to confuse customers repeatedly & consistently, whilst charging more financial funds from those paying customers: That is a 'manager's bonus & accountant's task to suit 'shareholder profit demands' joke with very low integrity and seems to be an intentionally organized, increasing download needs, & repeated Microsoft IT applied debacle. Stop those criminal activities and become a reliable service provider. (pls take time to read the attached terms & conditions (with a cheap lawyer, if you find a few hours of spare time which one could feel like wasting more on IT debacles)