Hi After Ian P's comment on the Forum I hope it's OK that I let you know that I have set Paypal up. It's at times like this when you realise how much Peter is missed. Any news ?
Some service providers accept everything and silently "drop" those that don't match a valid account in a misapprehension that this might inconvenience spammers (to be charitable towards those providers).
I think tella.com might be one such (they accept inactive addresses anyway). yahoo.com accepts everything too, so does gmail. But hotmail.com rejects (and I suppose, bounces) inactive addresses.
Once accepted by them, not many bounce undeliverable messages (it is bad practice) except the central Europeans who do things "differently". If your address (account) has ever been forged/spoofed as the "From:" or "Reply-to:" address of a mass-circulation spam to that part of the world you will know all about the consequences of that.
Using the "Verify email address" part of a service such as http://www.ipaddresslocation.org/email_lookup/check-email.php might help sort some of these out. After checking a known deliverable address (or formerly deliverable) in a particular domain that gets the green light, re-check with some improbable additional alphanumeric characters in the address and see if it is still accepted as "a valid deliverable e-mail box address."
Alas, nothing lasts forever - after a while the service providers get sick of such queries (maybe thinking users are spammers looking to validate addresses) and block them. [soapbox]The fools! - the most common, huge-volume, spammer "business model" simply doesn't care about validation these days (wasted "bandwidth" is horrendous).[/soapbox]
Anyway, that checker still works with the "majors" (yahoo, hotmail, gmail), currently.