Most academic colleagues use email addresses that end with .edu or .ac.uk, or related endings for other countries. But some (more often, younger people) use gmail, for example. I suspect that it is a mistake to do that, and that academic domain names are a genuinely good thing, simply because they help to certify the identity of the sender. I have a gmail address but I only use it for personal, not professional correspondence.
If someone emails me who is interested in a job or studentship with my research group, I give the message more credibility if it's an academic address (is it wrong to do so? I try not to be biased in how I respond to the message... but certainly there's a bigger risk that it looks, at first sight, like spam.) Or, if someone writes me a reference on behalf of someone else, the fact that it originates from a sender with a university email address is as good as a signature on paper - better in fact, since I don't recognize most people's signatures.
Is the above opinion sensible, or old-fashioned (or possibly, both)?