How to sync Thunderbird emails on Mac mini with iPad

Presumably you refer to the Mozilla Thunderbird Mail client App for your Mac mini? If so, just like the majority of Mail clients, Thunderbird will connect to your Mail Provider's IMAP or POP3 mailbox.

As such, while Mozilla have not released a Thunderbird App for iOS/iPadOS, you can simply setup and use your iPad's native Mail App. Both your Mac and iPad will connect with - and remain synchronised via - your Mail Provider's IMAP server.

Add an email account - Apple Support

it's the email account that keep the emails in sync not the email client, unless the mail account is the old pop3 type

in which case one can't really keep them in sync

you can read about IMAP mail account and how it automatically keep all clients in sync server side here

The Top 4 Differences Between IMAP and POP3 | Spiceworks - Spiceworks

Over the years, I have seen several friend's small businesses destroyed when their email provider chose to delete their email repository. I don't know why this happened, possibly as part of a software update, a software error or some malicious activity. For this reason, no one should rely on their email provider to act as a repository for email. The only alternatives I see are either to maintain one's own repository or to not keep a repository at all.

I keep my own repository and do my own backups. That has saved my bacon several times. With this approach, my email provider can clear out it's repository of my emails almost any time and I won't care or necessarily even be aware of their screwing around.

I did set up my iPhone and iPad native email client to access my email under IMAP. I was distressed to learn that when an IMAP client reads a message off the server, the message is deleted from the server. When this happens, the email is lost to any other device. This was clear from watching the ISP's repository via their web-based email client while the IMAP transactions were occurring.

This is acceptable if one does email on one device only. BUT, for anyone who, like me, wants to look at email from more than one device, this is unacceptable. As far as I can tell, this automatic deletion is part & parcel of the IMAP protocol. For this reason, until and unless I learn how to disable this unsocial IMAP "feature", I will stay with POP3.

I set up my iPhone/iPad to access email via POP3 but found that they seem to have some unfortunate and apparently undocumented couplings that keeps POP3 from working there. I have been able to read email, but sending does not appear to work. To be sure, my ISP has some security measures in place for POP3, but Thunderbird/windows handles them effortlessly.

Apparently, Mozilla does not yet have an iPhone/iPad version of Thunderbird. I have a collection of email sorting rules that are very effective in identifying "spam and sleaze" and routing them directly to my trash folder, so I'd really prefer an email client that can utilize my sorting rules or at least provide the facility to create such a list. Can anyone suggest such an email client for iPhone/iPad?

Transfer Thunderbird Mail from Mac Mini to I-Pad