Does one email address cut it? I'm a believer in creating as many email addresses as you need. Email addresses are so very easy to create and dispose, that it makes sense to have more than one. Working on a time limited project? Create an email for that time period. Need to exchange files or share emails with large content? Maybe a gmail or MS email would be useful to connect to a file sharing space such as Google Drive or One Drive.
Having at least two emails gives you the ability to add a second email as a security feature for services such as iTunes and others, where a second email address, unrelated to the first, can be used to authenticate the first email.
By setting each of these as an account in an email client such as Apple Mail, Mozilla Thunderbird, Outlook or Opera, you can easily manage them all in one place, create separate signatures for each, and transfer contacts between them, if needed. The only downsides I see is keeping them separated as appropriate, and managing multiple emails when travelling without a connected device. You should ensure sending to contacts from the appropriate email; it may not be best to send emails from your personal account to a corporate client. If you do not have a mobile device, and are using a friends or public terminal, checking multiple webmail sites may be tedious. However these days, most folks have a mobile device they keep with them which will easily allow managing email anywhere an Internet connection is available.
If you do set up multiple email identities, ensure you have a process of checking them on a regular basis. I suggest adding each to an email client, or automatically forwarding to an address you routinely check.