Outlook 2019

Probably. The biggest changes I had to deal with were with Office 2007 suite of applications with its ribbons then with the 64-bit of Office 2010 [first version generally available as either 32-bit or 64-bit], had to give up FrontPage 2003 as incompatible. Another change was the file format that added the x to the extensions such as doc to docx, xls to xlsx, etc. Both Outlook and Excel were available as individual programs. One issue I've read about seemed to be the E-Mailing from within Excel, worked best to first save the document then attach it to the outgoing message. Sharing files to those who use older versions sometimes requires saving as .xls which is 97-2003 format. There used to be a Compatibility Pack available for Office 2000, XP/2002 and 2003 for use with 2007 and later files.

See Install and use different versions of Office on the same PC - MSSupport

Denis