Calendar programme not synchronising

[#1]

I find the 'Inmydiary' free programme pretty good for jogging my declining memory as to what I need to be doing, every day at startup. The trouble is that I use both a Windows pc and an Android tablet, so needed to get them to synchronise. The diary programme has the facility to link with Google Calendar ( not tried yet) so it seemed that I should explore Calendar first and get that working (I thought !). So I now have Google Calendar installed on both tablet and pc, but as I favour Thunderbird, I picked up from somewhere that I also needed to install Lightning, which I have. I already had a gmail account, so with that on pc, tablet and phone, I was hopeful that I could get the calendar programmes talking to each other. Well, to a point, I have. The phone and the tablet seem to be in conversation, but aren't listening to the pc on which the diary is held. I don't know how, but when I set up the Google email, and created a Google account, it took it into its head to associate itself with an old Yahoo address very seldom used. Well, that keeps popping up here and there, I can find no way of removing the association, but have added my gmail account where I can. I am becoming worried that the harder I try, the worse mess I'm making. Loads on Youtube about making calendar entries but nothing in the way of setting the programme up for use. With gmail on all machines, I see no reason to involve Yahoo mail, but the latest obstacle is something called DMARK and the need to contact Yahoo. But I don't want to involve Yahoo, and would rather just concentrate on the Google's own gmail. But my problem is that even if some settings are found, I don't seem to be able to make any useful changes. It's a big 'ask' I know, but can someone give me a few pointers, please?

[#2]

Moderator's note(s):

Thread moved from Everything Else to Tech Help.

[#3]

@arktos 

I can't help with your various calendar syncing questions, but could the connection with the Yahoo address be because you entered it as a 'recovery' address when you set up the Google account (e.g. for logging in to an Android phone)?

[#4]

Thanks Rob,

I thought that you had something there, and found my recovery address on Google dashboard under security. It is indeed a Yahoo mail account, and the one I would have expected myself to have given. But it's not the one which appears in some settings pages, that is all but dormant. Can't see where to change the spurious one though, as the Google account page as above shows it as the one that I would choose today.

I see from reading around that this DMARC stuff is hassling a few people, but the apparent requirement to create some script and upload it to somewhere or other, is beyond me, and indeed seems to be expecting a lot from mere mortals. Especially as any publicity / implementation advice has eluded me.

Thanks for your input, which has focussed me on rationalizing these addresses, even if I currently can't see how to do it. Maybe I shall try to set gmail as my recovery address, - but I've seen suggestion that DMARC applies to that too.