This is why I hate forums for tech support. Yes, you guys are SO much smarter than everyone else. Obviously, we should ALL know how to do such a simple thing.
Let me give you a little on my technical background. First, I’ve been using, configuring, and supporting personal computers on a casual or professional level since my first Osborn in 1983. So I’ve been through the hassles of DOS and early Windows. I’ve also worked a little with UNIX and Linux systems over the years. I’m also a retired IT Consultant and ran institutional and personal networks for many years. I was never a programmer (had a couple of classes, but didn’t apply it professionally), but I’m also not the dolt you appear to assume that I am.
Simple fix, eh? Well here are the instructions I first found here in the “support” forum:
Open the Settings dialog: Menu > Tools > Settings.
Select Appearances > Themes.
Locate the theme you want to improve — one with the thin scroll bars.
Select it with a single click.
Click the dialog’s Advanced button, then select Save current theme as…
A standard Save dialog appears. eM Client supplies a default output filename ( Theme.emtheme ).
Pick a location for the file — and consider using a better name for it. Leave its extension as " emtheme".
The .emtheme file appears to be in a simple XML format.
Open the .emtheme file in a text editor — a programmer’s text editor, or even Microsoft’s massively powerful, state-of-the-art tool Notepad 
Give the theme some identifying information. I’ll use the Red Effect theme as an example. Locate this element near the top of the file:
<redeffectcolortheme name="" author=""></redeffectcolortheme>
Give the theme a name and, if you want, an author attribute — for example:
<redeffectcolortheme name="<b>Red Effect (better scroll bars)</b>" author="<b>John Q. Public</b>"></redeffectcolortheme>
Locate the " UseSystemScrollbar" element. Change this (note the text emphasized in boldface here):
False
… to this:
<usesystemscrollbar description="Use system scrollbars with no automatic <br />hiding"><b>True</b></usesystemscrollbar>
(I’ve wrapped the text here to two lines. In the file itself this XML element appears on a single line.)
Save the .emtheme file — as plain text.
Return to eM Client’s and select Menu > Tools > Settings > Appearance > Themes.
Click the dialog’s Import… button.
Select the .emtheme file you have just edited.
This imports the updated theme. To apply it:
Highlight it, click Apply , then click Ok.
These instructions aren’t clear, even to me, so how would users who have no technical background at all ever figure it out? In addition, the setting appears only to change whether the scroll bar hides or not. It doesn’t allow you to define the size or type of scroll . The problem that people on this forum topic are having isn’t that it hides, but that it’s too narrow to be easily useful for a number of users. And how would anyone know they could edit the themes in the first place? The buttons just say “Import” and “Advanced.” They don’t say “Edit Theme.” I guess users are all supposed to know this automatically, as you do, or else just shut their stupid mouths and make do?
All right, I could also just select a different theme. But I like the look of the Modern theme, apart from the tiny, nearly useless scroll bars. All I’d like to do is be able to define a pixel width for it that fits the screen resolution of my computer. Selecting a theme may be simple, but how is a user to know offhand that the various themes would include different widths of scroll bars? I suspect most users (and if you look at the forum listings, there are lots of people over the past two years who have found the scroll bars to be a problem) pick a theme more on the basis of its color and overall appearance and probably never notice that the scroll bar widths vary with the themes. Besides, if I like Modern, why can’t I also have the ability to tailor certain details (various colors, fonts, scroll bars, etc.) to my liking?
So you both seem to have missed my point entirely: Why should the user have to go to any trouble at all? When you build a product, wouldn’t you want to make it as user-friendly as possible? If a number of people have been reporting problems for two years about using these narrow scroll bars, wouldn’t you think that developers should have responded by now to provide a simple solution besides having to choose from locked-down themes?
As I said originally, eM Client is a nearly perfect application, and it’s no surprise to me that they can boast 1,000,000 users (I’m surprised it isn’t more!). Let’s say that maybe 1/3 of those users use laptops or tablets, most of which these days have high resolution displays. So possibly up to, say, 300,000 eM Client customers could be potentially dissatisfied with the width of these scroll bars. Why should it be up to so USERS to have to tinker with script coding or be restricted to a limited number of theme choices? Why NOT make it simple either to just right-click on the scroll bar to set a width (either by number of pixels they choose or at least two or three options, like “narrow,” “medium,” or “wide?” Or why not just make the details of the themes editable in the interface, so that for any given theme a user could choose colors, font styles and sizes, scroll bar widths, etc., etc. Or do away with themes altogether and simply let the use tailor all aspects of the interface to his or her desires.
From the number of postings in this forum, it appears there is a significant issue for people having to do with the narrow width of the scroll bars in v.7. After two years, it seems to me that the developers should have addressed it, that’s all. So I’m just prodding them. I love the product (in spite of my frustration with the skinny scroll bars). I respect the developers. I’m just asking for eM Client to become even better and address users’ real concerns.
Please accept my apologies if I sound a bit annoyed with your responses here, but your tone (both of you) conveys an attitude (“it’s SO simple – what’s wrong with you?”) of superiority that is unwarranted and typical of many techno-geeks who may themselves love to get into the guts of computers and figure out how to put 'em through their paces in novel ways. But, believe me, MOST users don’t want to fiddle, they just want their computers to work in a simple, straightforward way. The fact that they may not know or want to spend hours scanning forums for answers to simple technical issues doesn’t make them any less intelligent or important or valuable than those who do. In fact, it could be argued that the opposite is the case – that techies who use their know how to make things easier for ordinary users who have issues are the real gems.