I think you mean that the installer checks for and fetches an updated TB? I wasn't aware of this behavior (but I've never tried installing an older version).

I suggest that you download TB and then disconnect from your network before installation. Then go to tools > options > advanced > update and select either the "check" or "never" to prevent updates in the future.

Using a laptop, it's easy to disconnect from a network. If you're using a Windows desktop, I'd probably use a system command:

Click Start->Run, type cmd and press Enter. Type ipconfig /release at the prompt window and press Enter. This will disconnect you (unless you use a static IP, in which case you know all this already). Type ipconfig /renew at the prompt and press Enter to re-establish a connection (which takes a couple minutes for the DHCP server to respond).

According to the release note the latest version fixed the mapi issue. Have to tried the newest version? https://www.thunderbird.net/en-US/thunderbird/60.5.2/releasenotes/

60.5.3 has further fixes.