Regretfully or regrettably?

[BerylStreep]

If you were sending someone a 'sorry, no' e-mail, would you say regretfully I can't ... or regrettably I can't ...?

[Goldmandra]

I am regretful. It is regrettable.
It depends which one you mean.

[BerylStreep]

Regret I don't think it appropriate to have a meeting with you.

[NigellasDealer]

regretfully

[prism]

Say "I regret that I can't", then you will also avoid the adverb-as-modal-adjunct bear trap. Assuming, of course, that you actually can't, as opposed to not wanting to, and you really do regret it.

[BerylStreep]

Thank you.

It would possibly be more accurate to say 'There's not a chance in hell that I'm going to meet you.'

Unfortunately we are bound by niceties and professionalism.

[Middleagedmotheroftwo]

isn't a particularly well constructed sentence, from a gramatical pov.

Better to say

[BerylStreep]

Thank you Middleagedmother. The e-mail is already sent, but I think I knew it wasn't that well phrased.

I am a complete pedant when it comes to spelling and punctuation, but I could probably do with some refresher classes for grammar.