A letter or email is always from the sender and to the receiver – never of.

WRONG
We would like to present our standpoint regarding the email of the Company dated 28 January 2011.

RIGHT
We would like to present our standpoint regarding the email from the Company dated 28 January 2011.

WRONG
In connection with receiving, on 11 March 2011, a letter of the Tender Committee announcing the completion of the second stage of the tender proceedings, please be informed that …

RIGHT
In connection with receiving, on 11 March 2011, a letter from the Tender Committee announcing the completion of the second stage of the tender proceedings, please be informed that …

The construction “the letter of Anna” is un-English, but it would be understood to mean “Anna’s letter”. Without any context, this tells us nothing about whether Anna wrote the letter or received it.
“The letter to Anna” means that Anna received it, while “the letter from Anna” means that Anna wrote it. Only use the construction “Anna’s letter” if it is clear from the context whether Anna wrote or received the letter.

This rule also applies to notifications, messages and other forms of communication.