I'm not sure if it's the only, or best, way but I use my mail host's caldav and carddav service for that.

First, check if your mail host provides caldav and cardav service. If they do, they will probably provide instructions for configuring thunderbird to access them.

Once that is done, thunderbird on both your machines will periodically synchronise, thereby sharing your events and contacts via the host's service. It also means you can access your calendar and contacts from most mobiles, even if they don't support thunderbird.

If your mail host doesn't provide the service, then you might be able to set up caldav and carddav on your shared network device but I suspect that would be a lot more complicated.

Hallo harry, thanks for your feedback! My cloud provider does not offer caldav and carddav service. My idea was to set up a profile which is pointing for calendar and adressbok to this drive. But I am not an expert - may be it can be a solution?

I think that might be risk data corruption, especially if the two PCs both try to access thunderbird at the same time. A system intended for multiple users would ensure that if two people try to update the same database or variable at the same time, their changes happen sequentially or in a co-ordinated fashion, rather than both writing to the same record and one of them deleting the other's work. Thunderbird is designed for a single user, so it's unlikely to be implemented that way,

It could possibly work if the two users were "me, when I', at work" and "me, when I'm at home" so that the twothunderbirds never get used at the same time. But even then, there's a danger that you accidentally leave thunderbird open when you go home and possibly then thunderbird might not let you back in at home.

Hello harry, thanks for you feedback - your arguments conviced so that I have to find a solution with a system running as you described. Do you have an idea in which direction I should investigate to find a system? I know it should not be from Google, Microsoft or Apple as my intention is not to use these big companies.

I can describe how my system works.

It's based around thunderbird, which I have used since I registered my own domain name in 2013 but I used thunderbird with other email addresses for many years before that.

It's not essential to register your own domain name. But owning an email address in the form *.myChosenDomain.org.uk has some advantages over an email address like onefixedname@somespywarecompany.com:

• it's a wildcard address so I can instantly create additional addresses like info@myChosenDomain.org.uk or 2026party@my..... if I want a separate mailbox for them.
• the domain is owned by me, not by some spyware company, so if the company hosting my mail service increases the price, becomes unreliable or even goes out of business, I can move to another mail host without having to tell everybody a new email address.

I'm using netcetera as my domain registrar, but you can use any reliable registrar that provides a name-only service at a reasonable price.

Nevertheless, you can stick with the email address provided by your existing mail host if you wish -- provided it has well documented support for SMTP and IMAP so that thunderbird can send and receive mail through it.

I have a collection of old laptops, some of which occasionally run thunderbird. They each have separate thunderbird profiles, sending and receiving mail via my mail host's SMTP and IMAP service.

My android (lineageos) phone previously used the built in mail reader but a few years ago I replaced it with k9 (which is now operating as part of mozilla -- see https://k9mail.app/2023/12/28/When-will-Thunderbird-for-Android-be-released). This works similar to thunderbird, sending and receiving mail via my mail host's SMTP and IMAP services.

My current mail host is mailbox.org. I've only used this for a few months, when my previous mail host for many years "enhanced" its mail software and became unreliable. So far mailbox is working well.

My calendar has always been based in thunderbird, so when I started using mobiles it was logical to find a caldav service so the two could share data. My mail host at the time did not operate caldav so I created an account with GMX and used that until a month ago, when one of my three calendars refused to accept new entries from firefox. It was the biggest of my calendars and I think it might just have grown too big for GMX. Mailbox provides a caldav service, so I transferred the calendars across to it and that too seems to be working well. At the same time I transferred my contacts from GMX to mailbox.

In summary, everything is now either local instances ( thunderbird on windows, or k9 on lineageos/android) linked using mailbox.org SMTP/IMAP/CalDav/CardDav).

That said, setting up something like the above does involve a learning curve if you haven't done it before. My time over the next four weeks is going to be limited because of a special event that's coming up, so although I'll keep an eye on this thread it might be wise to do only initial tests until you're comfortable about it working as you need.