The title and first post don´t match.
Do You wish to change email providers ? -- as per title ..
or email addresses .. as per OP explanation.
Details are critical in IT stuff.
And in machining or engineering.
1. IF you have an email address like
[email protected] it is easy to change providers.
2. IF you have an email address like
[email protected]_domain_name.com it is still fairly easy to change providers.
You can use a workaround.
You yourself can setup an automatic forwarder and an automatic reply, from the old subdomain / mail address.
Typically, something in auto-reply like "the email address has changed. Please use
[email protected] in the future".
But
ALL the old-address emails will still come to you.
You just need to pay the 200$ or so for a year for the old email service, until everyone has gone to the new email address.
You just setup a forward / redirect / copy / bounce from the old address to the new email address.
And an auto-reply advising the sender to change to the new address,
and a second one to Yourself to remember to check up on them to change the email contact details.
Endless technical options, and most don´t require any real money or real IT or internet skills.
And multiple options do not require your old ISP to participate at all.
You could read your "old" email address every one minute, and auto-forward and auto-reply to each email as per above.
Using an old dedicated obsolete pc, 30$, to do so, 24x7x365.
Since your email volume is tiny in "´net" terms, it would work just fine.
You can/could use MS outlook (yuk for security) or any email client + script you like.
The server-based solutions for same were above 700 emails/sec back in 2002, even 15 years ago when I was in the business industrially.