Wouldn't bother going back much further than 14 months in an initial review. If you haven't needed to interact with an account in that time then its probably no great loss.
Good luck with the migration, it is a pain.
Hi @petergdownload. Yes, I understand what you're saying, and you're right that most of the address changes will not take much time, and that more recent inbox entries are almost certainly the most relevant, But I also have some older things I have to dig into a bit, and I simply want enough lead time to make sure I cover it all off.
In my work, and over time generally, I have purchased numerous software subscriptions - the old type where you download an application to run on your local PC, and receive updates along the way.
One of these I've owned since about 2004. I receive two emails from this mob, and both emails are subscribed separately from my main software account, but I've rarely accessed the actual account with the software supplier by logging into my account with them.. So I have to change the email address on both regular emails, but that's not such an issue.
It's more the audit of all of these software subscriptions, missing none of them, and then logging into ancient account details and changing the email address I used at registration / initial purchase, maybe proving who I am after such a long time, making the change somewhere, then validating new address etc etc that will take the time. If I ever needed a password reset, for instance, the PW reset details could be sent to a dead email address and so forth. Also, account verification could be an issue if I ever needed to talk to the company or get support (some support systems rely partly on matching the incoming email address with their account registrations etc). So I'm best off changing these details now, before I run into future troubles - and as I say, there's a *lot* of this, and it goes back a long way, and I expect moderate levels of messiness.
But yeah, most of the day to day stuff I can knock over in a reasonable time frame, and I'll also take the opportunity to cull and virtually unsubscribe from some emails by simply leaving them back with the optusnet email address, and not porting to my new one - having this ability is one argument against email forwarding, which I will avoid if I can.
Perhaps set up a second gmail address? Set it to sync every Optus email you ever got in its settings. Also do the forwarding thing to this email. That way when Optus goes dark you have everything possible secured. Means you don't have to be quite so thorough ticking off everything as you still have a reference you can dip into if needed.
Gmail can also link multiple accounts to the main web interface so you can swap between them in a click without getting them mixed up together.
Obviously when you're ready, cut the reference account loose.