There are a lot of good free email services out there but I am not satisfied with their spam filters. I am getting about 300 spam mails a day and with my current solution only one of them makes it into my inbox per month.
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The second reason is that I do not want to delete or archive my mails to often and I want to have access to them anywhere at any time. Therefor I need an IMAP server with a lot of storage. Most free mail services provide this nowadays but did not five years ago. I thought about using GMAIL lately but I am not completely happy with storing all my mails on Google servers.