The mail will sync if the accounts are set up as IMAP on all computers, and even with devices such as phones that don't run TB. Calendars and contacts can be synced if they have a network calendar or address book installed in Lightning, with an add-on like TbSync.

Thanks for your reply. The version TB I downloaded and installed is 68.6.0. It already has a calendar included. Is the installed calendar the same as Lightning calendar, or do I have to download and install Lightning separately? Again, thanks.

The installed calendar is Lightning, and you can create a local calendar or a network calendar such as the ones provided by google or outlook.com. Local calendars, of course, don't sync with other computers. Using an add-on is the simplest way to add a network calendar, and if you do this on both computers, the calendar is synced.

https://support.mozilla.org/en-US/kb/using-lightning-google-calendar

OK. Got it. Thanks!!

Hello,

My laptop and my desktop PC's are set up as IMAP but they do not sync with each other so is there a way to have the same setup on both and have them delete messages on both no matter which PC I am using? I know that they will both sync to the same server (Outlook Mail) but I want both PC's to sync with each other too as far as Thunderbird is concerned.

Thanks!