Letter writing

[Unregistered]

I understood that one should use sincerely as a close when opening with a Christian name. When writing either Mr/Mrs x or Sir/Madam use faithfully. Is this correct?

 

[Horsa]

I'm afraid not.

The convention is -

sincerely with christian name and Mr/Mrs/Miss/Ms

But

faithfully with Madam/Sir(s) etc.