almost all email providers include an option that you can set to redirect the emails to another account.
This is useful if your email provider does not provide an efficient spam filter that cannot learn who you want to read and who you don't want, and that does not include an option to signal spams so that they won't go into you inbox.
I've redirected my oldest email address (created 20 years ago in 1995) to Gmail and Gmail does the job of filtering all according to my needs, and I can also set rules to sort automatically some mails to specific folders (first create a "label", then instruct Gmail to classify those mails coming fromthe same source to the labeled folder (Gmail checks the MIME headers to assert if this is likely the same sender or if it has been abused with a fake sender address).
Then you can read emails either from the online inbox, or with a local client supporting secure SMTP and secure POP3, without having to constantly download all the junks that are going to the "undesirable" folder (you may just check it sometime when you expect a new email from a new site sending you a confimation and this does not come in the next few minutes. That folder (and the "deleted mails" folder) is automatically managed and old emails stored in that folder are deleted automatically after 30 days (but you can also empty it yourself.
Gmail is fast and troublefree. It also has the advantage of not binding you yo your current ISP (many of them will delete your mail address when you swiich to another ISP). It is the perfect way to be contactable ny family and near friends for many years. It is also the email adress you should use when subscribing social networks.
Additionally it offers a considerable storage space (my own Gmail account has stored all emails I kept since more than 10 years and I'm far from the storage limit (only 1% used for the 115GB private storage offered to me by Google for Gmail or for other Google webspaces !), even if the account receives about 15 000 emails each month on average (most of them are deleted, I don't always signal them as spam because I have subscribed them but I read them occasionnaly and delete many that are repeated too frequently (including emails from Cnet itself !).
Most emails are deleted after just looking at a sender that I don't want to read for now (even if I have subscribed it): the only thing I may read is the subject line. Thanks, Gmail authenticates most senders, and also identifies correctly most spams (because it learns from spams signaled by its very wide users community).
The result is then manageable and I'll just have a dozen of new mails coming when I connect to Gmail.
Then most unsorted mails (that have not been sorted automativally by Gmail with its spam filter or my own "labeled" filters, or not following as a reply to a mail I snet myself, or from a discussion that I marked as "important" (to avoid it being incorrectly sorted as spams, notably from some interesting mailing lists) will be read once and deleted just after, even if they were interesting. I only keep those related to bought products and specific mailing lists to which I participate and I read regularly (also if I cannot read them immediately, they are archived in their own folder that Gmail sorts automatically with the "label" I defined for them (sometimes I'll look in the archives to find a past related discussion).
I've abandonned local storage by email clients, all emails are archived online and I read them with a webmail. This is easier when switching everyday between the smartphone and one or several PCs. It really took too much work locally, it was a nightmare when switching PCs, I lost several times my archives when I had to reinstall the system.
If you use Thunderbird, configure it to use POP3 (or better IMAP which downloads emails only on demand and allows you to see the folders), so that it won't delete emails on the server as soon as they are downloaded to your local PC (this is the default option for most local email clients). Or use it locally only once you have processed all the incoming emails and you no longer want to access them later from all your devices (including your mobile or from a PC owned by a friend or family member you visit, or from some remote site offering you an internet access, for which you are confident that it is secure enough, check it first!, with a new private session with a temporary user account) but only at home with your local storage (but you'll have to maintain yourself the backup of your archives, and their transfer if you change your PC or have to reinstall it).
Webmails also allow easy clearing of your tracks when you have used a PC owned by someone else: clear the browser cache once you have finished (but before that, make sure that this PC has a running security suite, that its system updates are OK, that the browser is not overcrowded with too many bars and extensions (look into the extensions options of the browser, if you don't know them, prefer not using this PC or ask to the ownser if you can cleanup things first and perform the long waiting system updates, however in most cases, you don't have the time to do that : use your own smartphone that you manage yourself, and if you want a biffer screen, forward the interesting emails to the address of the PC owner to read it in its own local configurationm do that only if the email does not contain personnal information such as autologin parameters to your online account for the website you want to visit)
I no longer see any interest in local mail clients from all brands in all OSes that depend only on their local storage. I want my mails to remain online, stored by the mail provider (it has other benefits such as helping you to better sort them according yo you real usage and desires).
Gmail is also different from many webmails in the fact it does not force you to read ugly ads everywhere in its interface (there are only small announces related to the sender, when it is commercial, for exampel when reading the emails from the Cnet mailing list, you may see sometimes some announces from Cnet, such as the offer to follow its page on Google+ or Facebook, or that you can print on your contact cards, or when contacting an adminsitration or bank, because Gmail will authenticate these organisms and protect you from alsmost all phishing attempts using fake senders)
But for some new retailers you still don't known, as everyone, I suggest you make the first purchase using a new specific email account (you can create one for free on many webmails such as Yahoo Mail, Microsoft Live Mail). Once you get confident, and find interest in the few emails the send you (even if you don't read them always) you may register with a more permanent email account. If the intent is just to receive the confirmation of a single purchase; use only your junk mail address online (you don't need to configure your local client to read these temporary emails)
Some providers allow you to create as many temporary email addresses you want and at any time, while still forwarding them to your account with an indicator identifying the initial email you created. Once this email address is compromized (it will always happen sooner or later), you'll have to drop that adress or just keep it in its own folder not mixed with the rest in your main inbox (if you still want to read later a few of these mails from this sender). It will save you much time.
Note: it's not necessary to signal all spams that have passed your current filters. use the search function in Gmail to locate them more easily, create a selection and push the "signal as spam" button once. They are automatically moved to the same folder storing the undesirable mails that have been filtered autmatically. Keep these mails there, this will help Gmail sort other frequent mails coming again and again from the same source. Gmail will cleanup this folfer automatically for you and during the 30 next days, all spammers will be detected (it's rare that spams are sent only once in a mounth, because they use legions of bots to send you multiple copies hoping that these bots will not all be detected)
For this reason, on Gmail it has become extremely rare that I can see some real spam getting unfiltered to my inbox (not any one for months, or sometimes 1 or 2 from a new source that I will signal, and never hear again, as they will go to the undesirable box automaically; ma,ny other Gmail users wil have signaled also this same source to Gmail). Even for my Gmail address that is now public since several years; or spams sent to my main 20-years old email address which is redirected to Gmail; and that I could keep because my old national ISP allowed me to contjnue using it for infinite time without paying anything).