That's something folk tend to not get into. Since it wasn't secure in the first place, you have a bigger issue to tackle.
Now when we do have a secure email system, what happens? Please read https://en.wikipedia.org/wiki/Lavabit
Now if you didn't mean "secure" but had a leaked password, you may want to consider changing it on all your devices and stop storing it on all devices. Painful but it may be required.
How to make email secure after hacking

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