Use it or lose it.
If you don't log into your email account, the account and all the e-mail contained within it might eventually get deleted. It happens with most email services, but the question is: how long does it take?
After 360 days (five days short of a typical year) of inactivity, a Windows Live Hotmail account is permanently deleted. If you don't use your Windows Live ID (which is your Windows Live Hotmail email address) for 365 days (about a year), it, too, can be permanently deleted. Somebody else can take your Windows Live Hotmail address!
A Yahoo! Mail account will be deactivated automatically after 12 months (1 year) of inactivity. To ensure continued use of your account, it is best to log into it using a desktop browser at least once a year.
A BT Mail account will be permanently deleted after 60 days without further notice - once deleted, your email address and any personal data held in the mailbox can't be recovered
If you don't log in to your AOL Mail account for 90 days, the account is deactivated. If you don't log in for an additional 90 days—for a total of 180 days—the account is deleted. You may or may not be able to reclaim the email address later. Even if you can, the account will be empty and your emails previously received or sent gone.
As of late 2017, Google does not automatically delete inactive Gmail accounts. The company reserves the right to delete accounts that remain inactive for an extended period of time but does not usually do so.
So far, Gmail seems to be the winner. Do you know of any other email providers who'll keep your account alive for even longer? Have you got any horror stories about your email being deleted?