We are writing to inform you that ...
to confirm ...
to request ...
to enquire about ...I am contacting you for the following reason.I recently read/heard about . . .and would like to know . . .Having seen your advertisement in ... , I would like to ...I would be interested in (obtaining/receiving) ...I received your address from ...and would like to ...I am writing to tell you about ... Thank you for your letter of May 13 ...Thank you for contacting us.In reply to your request ...Thank you for your letter regarding ...With reference to our telephone conversation yesterday ...Further to our meeting last week ...It was a pleasure meeting you in London last month.I enjoyed having lunch with you last week in Tokyo.I would just like to confirm the main points we discussed on Tuesday . . .