If you are going to sound human and sincere in your letters, avoid superfluous and stilted expressions. Hackneyed and vague wording gives an impression of being offhand rather than polite.

NOT THIS ALTERNATIVES
Starchy beginnings
 We respectfully acknowledge receipt of...
 I have to acknowledge with thanks...
 Yours of even date to hand.
 We have pleasure in attaching...
 Referring to your communication of...
 The above mentioned...
 We note your comments regarding...
 The contents of which are noted...
 This letter is for the purpose of requesting...  Thank you for...

 Thank you for...
 We have your letter of the same date
 We attach...
 Concerning your letter of...
 The... mentioned earlier
 We note what you say about...
 (or leave out)
 We should be grateful if...
Pomposity
 We beg to advise...
 It will be appreciated that...

 It is suggested that the reason... .

 The undersigned/writer...

 May we take this opportunity of...
 Allow me to say in this instance...
 Which you claim/state...

 For your information...
 We should point out that...
 Having regard to the fact that...
 Answer in the affirmative/negative...
 We are giving the matter every consideration
 We are not in a position to...
 The opportunity is taken to mention...
 Despatched under separate cover...  (leave out)
 You will appreciate that ...(or leave out)
 The reason, we suggest, is ...(if courtesy needed)
 The undersigned/writer (necessary if writing for the company "we")
 May we ...
 (leave out:)
 Which, in your view, (where one is disagreeing by implication)
 (leave out)
 (leave out)
 Since...
 Let us know whether... or not
 We are considering the matter

 We cannot...
 (leave out)
 Sent separately
Coldness and bad psychology
 Advise/inform
 Desire
 Learn/note
 Obtain
 Regret
 Trust
 Your complaint/dissatisfaction

 Dictated but not read by  Tell
 Wish
 See
 Get
 We are sorry
 Hope
 The matter you are taking up with us (or you raise)
 Dictated by... and signed in his absence (or separate notification in the body of the letter)
Cliché endings
 Thanking you in advance
 Assuring you of our best attention at all times, we remain
 Regretting our inability to be of service in this matter
 Trusting we may be favoured with...
 Awaiting a favourable reply
 Please do not hesitate to...
 Thank you once again  (leave out)
 (leave out)

 We are sorry not to be able to help over this
 Please let us have
 (leave out)
 Please...
 (leave out)