The real issue, IMO, is being contacted out of the blue by a provider when I haven't asked her to contact me. It's one thing if I say to a provider (especially a visiting provider), "Hey, I had a great time with you! Next time you're in town, I hope you'll shoot me an email." But if every provider I've ever seen felt free to send me emails whenever she wanted to stir up a little business - well, it wouldn't take long before I sent all their emails to the SPAM folder.
Regardless of whether any significant other has access to an email account, it's just not polite to keep contacting a client after the encounter is over. If I've already seen a provider, I have her contact info anyway, and I can go ahead and make the first contact move if I'm in the mood for a little company.
Email access isn't just about hacking. If someone gets a phone call and steps away from their computer, they may accidentally leave the screen on. It may ultimately be the client's "fault," due to their carelessness, but that's no answer to the turmoil that would ensue in their primary relationship.
A provider-client relationship is unique: It's not the same as a real estate agent contacting a client on her own after she's sold him a condo. By its nature, a provider-client relationship calls for a higher level of discretion. It may indeed be wise for me to set up a 2nd email account for provider contacts, but the issue isn't just "Do I have a safe account at which I can receive emails?" The issue is that many clients do NOT have the sense to establish a 2nd email account. Does my visiting a provider mean that I am inviting future emails indefinitely?
I'm simply discussing this issue as a matter of professional courtesy. A professional would ask her client, "Is it all right with you if I send you emails about my availability from time to time?" That single question is all it takes to clear up any misunderstandings, even if it's just 1 guy in a dozen who might not understand that after contacting you once, you're going to be emailing him, on your own initiative, in the future.
Is it possible to keep one's email secure? Yes, it is. Is it relatively easy to do? Yes, it is. Are there hobbyists who don't think that far ahead? Yes, there are, even in this day and age. Is it ultimately their responsibility if they leave their computer screen on and their SO catches them? Yes, it is.
Is it difficult to ask for the client's permission first? No, it isn't. Might it avoid a HUGE amount of harm to a technically unknowledgeable client in the future? Yes, it might.
Professionals act like professionals. When I hand offer a professional lady a rather significant "gift" in return for her company and services, I shouldn't be able to expect the minimal courtesy of being asked for permission before she contacts me in the future. I may have enjoyed my encounter with the lady and may be looking forward to the next one, but unlike dating - where it is obviously, perfectly acceptable for the lady to contact the gentleman to ask about the next date - providers and clients are in a very discreet, commercial relationship. It's the professional - the provider - who ought to act professionally and obtain express permission for unsolicited email contacts in the future.
BostonBob