I am the power of attorney for my 77 year old relative who has dementia and is in an assisted living facility. Since I am also 77 and the only relative I am worried about the need to hire someone to care for my cousins financials, insurance, etc. if/when I become unable to continue. Our attorney wasn't able to come up with a solution and when I read the description of professionals who could handle dependents' affairs I was excited. Unfortunately I somehow deleted the email and can't seem to retrieve it.
Regarding your email, there should be folders where your mail is stored. On my Macbook Pro, it is in the Mail function and a deleted email goes into my Trash folder. You can also go to YouTube and type in the search, "How to find a deleted email on a (list your type of device)" and an instructional video will probably exist to show you. Good luck!
You can also contact your e-mail service provider and ask them to search for an accidentally deleted e-mail. But if it's Comcast, don't bother; I just went through that and got nothing but worthless advice.
I would think that all e-mail servers store information on backup servers or what's more commonly referred to as the "cloud". Question is whether or not they'll bother. I think it would depend on your ISP.
Another good practice is to immediately print, save to your hard drive, or offline storage (disk, hard drive) all those kinds of e-mails with helpful information.