winebrowser mailto opens Linux browser not mailer

[Elizabeth Lock]

I use Wine to run MS Office 2003 with a lot of fairly complex VBA. Most of it works, but when I send a mail message to winebrowser mailto in Access VBA it now gets opened in Firefox, not Thunderbird.
<code>
Dim DoMail As Long
DoMail = Shell("C:/windows/system32/winebrowser mailto:" & EMailAddress & "?subject=Blah" & stSalutation & stText ... etc
</code>

Composes message correctly in Thunderbird under Wine 5.0.3 but goes wrong in Wine 6.

I am using Lubuntu 18.04 LTS; I can tell you the overrides and winetricks installations necessary to get Access VBA going if you wish; it's fairly involved.

I have had to roll back to Wine 5.0.3.