How difficult is exporting from one provider into another (e.g. from gmail into proton or purely)? I guess normies like me are a bit hesitant due to the risk of messing it up (would be a disaster to lose years of emails, as some are important for record-keeping). Curious to hear from people who've done(/attempted) it and how it went? Was it hard? Were there risks? Any regrets?
I can't speak for Purely, but every one I've tried has had an "import from [previous provider]" feature because that's basically just "pull from imap".
Otherwise: for ~20 years now I've been able to just attach two imap accounts in thunderbird, and drag to move/copy everything from one to the other, and that'll just chug away until it's done. I've never had an issue doing that.
After trying to do this many times using scripting or even paid services… i came to conclusion that easiest and most reliable way is to add both accounts in Thunderbird and copy paste the emails.
If your provider supports IMAP, you can use imapsync https://imapsync.lamiral.info/ to sync emails between two mail boxes. I did it a few times and it was straightforward.
For libre options available from Linux distributions' repositories, see isync (aka mbsync) and offlineimap. And mail clients in general should be able to handle IMAP and standard formats (Maildir, mbox). If one cares about mail backups, it is also useful to archive and backup one's mail in one of those standard and portable formats, and/or to synchronize between multiple machines regularly.
Last year I migrated from my hosting providers email service to Proton Mail after 20 years. I too was worried about preserving mails.
I have used Thunderbird for everything, set to download everything and never delete, so had my primary backup there. I take regular backups of the profile directory as secondary measure, which are kept on my NAS and offsite.
What I did was to just decide to do a hard break. I renamed the old IMAP accounts, added the Proton Mail accounts using the IMAP bridge, and then configured my DNS to point to Proton.
DMARC and all that was easily set up as well thanks to Proton having nice guides and active verification.
Now I still have access to my old mail in my old account folder, and I can use the Proton Mail app on my phone for new stuff.
I also migrated a secondary mail, which was not using my domain and which I've had for almost three decades. There I had to do the laborious task of changing any accounts tied to it, and notify people still using it. I've been keeping it operational for a year and still get the occasional mail, but at a point where I'll be retiring it soon.
Overall been very happy. It showed me it was easier than I feared as long as I have Thunderbird and mail accounts under my own domain.
From one domain to another (gmail.com to custom), a bit of faffing about to get all the accounts moves over.
Moving the mails was as simple as ctrl+a and dragging my mouse in thunderbird.
Between providers with a custom domain (zoho to mxroute) was easy. Just updating the DNS records and moving the emails.
If you are technically able (really just buying a domain and setting the DNS records the provider tells you) I would recommend getting a custom domain. It gives you the ability to move providers at will pretty easily, even if you did want to stick with a gmail for now.
Pretty much every "normie" should download and setup an email client like Thunderbird. You can open it once a month or so to let all the emails download to your own computer. Possibly backed up by some cloud service.
Should be sufficient unless you lose your computer and your email account gets blocked at the same time.
I migrated from Fastmail to Proton last week. I found the whole process pretty painless. Proton has an IMAP migration. Took it a few days, maybe even three. But everything ended up working just fine.
