I was happily using Pegasus Mail 4.73 on Wine on Linux Mint 19.3 Tricia without any problems at all.

Then a Wine upgrade (to 7.13) arrived. I haven't recently had problems with Wine upgrades so I happily let it do its business. Hindsight says different!

The scroll bars wouldn't work, any of them. No problem with the folders box as the mouse wheel still worked. Similarly with the list of emails. Problem with the message box, as for ages the mouse wheel hasn't worked for fancy formatted messages, so losing working scroll bars there is a bit of an issue. Sadly most people nowadays don't understand that email is intended to be a plain text system.

Knowing that I'd get short shrift on a Wine forum unless I was using entirely the latest of everything, I "upgraded" to Pegasus Mail 4.80. All within the new Wine. And now it won't start at all!

Am I alone, or is this a fault common to others?
If others have fought their way out of this, any tips to pass on?

Many thanks for your time and help.

I do Wine but only as a beverage. That said, I did play with it years ago and back then Pegasus Mail would not start if IERenderer was in the picture. I think disabling it would be worth a try until a Wine user chimes in. To do it, locate the IERenderer.fff file located in \Pmail\Programs and rename it to something like IERenderer_fff.disabled.

Haven't seen the 7.13 version yet.
wine-7.10-2.fc35.x86_64 is the version that Fedora Repo still has in standard repos.
Generally agree that the Pegasus works fine under wine, but IERender doesn't work with wine.
It will load, but it must make some calls at some point that are not fully supported.
Can use the uninstall program in PMAIL/Programs usually with name like unins000.exe.
The will generally remove IERender stuff, but sometimes directory and 1 file is left.
Can then manually remove it.
I've also had some issues with the Bearhtml not working 100%, and find removing its DLL also works better at this point. The 4.80 has upgraded the TER/HTS programs and they handle the html code much better than 4.73 versions did.
Will watch for Fedora to come out with updated version, but would suggest trying to remove the IERender first, and then just rename BEARHTML.DLL, and see if that fixes issues.

I get my Wine direct from the WineHQ repository. The Distro versions can sometimes be quite a while behind.

IERenderer has been a Wine no-no for ages, so I had disabled it. I had forgotten that a WinPM upgrade would re-install it. Thanks both of you for the reminder. Now done and it restarts. Good.

But I am still without working scroll bars for the folder list and the message list. The message pane scroll bars do work. Does anyone know what calls WinPM makes to the OS or to other dlls to get scroll bars to work? Knowing that might help in the inevitable negotiation with the WineHQ crew.

However the message pane is only useful in plain text mode and even then it sometimes looks very similar to the attached image. Any attempt to read the "pretty" version is "pretty awful" as in the attached image.

Many thanks.

PS In WinXP it works OK.

I generally stick with the repo version of programs on my notebook and most machines. Have sometime used direct versions for testing. So no issue with repo version of wine that is at wine-core-7.10-2.fc35.x86_64

Checked what updates-testing has and it shows they have 7.12-2 in it.
dnf upgrade wine* --enablerepo=updates-testing
Fedora 35 - x86_64 - Test Updates 1.4 MB/s | 7.2 MB 00:05
Upgrading:
wine x86_64 7.12-2.fc35 updates-testing 12 k

So didn't actual install it, so said N at end report of what would be installed.
43 wine packages and 2 mingw ones.

The attached image is weird. I see an H at top of body in box, but shows just one character.
Curious, and you using the Pegasus build in SSL? With 4.73 had an issue with connecting to gmail since it had an older version, so setup Stunnel and setup local IP routing to have Pegasus connect thru the stunnel for both gmail and local ISP. The linux has a newer version of OpenSSL and is 64 bit versus the Pegasus one that would be 32 bit, but that would have no issue with scroll bars.
Have mine set to emulate Windows 10, but never saw a difference. Wonder why the XP option worked. Perhaps they did some change that was for 10/11 that broke something.
Will see if they release 7.12-2 from standard repo soon, or might wait for later version.
Good Luck.