This is my letter to the World

This is my letter to the World
That never wrote to Me —
The simple News that Nature told —
With tender Majesty

Her Message is committed
To Hands I cannot see —
For love of Her — Sweet — countrymen —
Judge tenderly — of Me
                                   F519 (1863)  J441

                                                     
This is among the most quoted poems among Dickinson scholars. I find it lovely and tender – in fact, tenderness is a part of the poem itself. While some scholars milk the first two lines for a bit of bitterness on Dickinson's part, my own reading of the poem is in line with Helen Vendler's. Dickinson is writing to all the peoples whether of her own age or ours or some distant future. The poetry she entrusts to future hands, the ones she "cannot see," is that of nature. As nature's poet, she hopes her "countrymen" will judge her "tenderly."
It's a humble thought. As Vendler puts it, Dickinson is implying that it is her theme and subject that elevate her poetry rather than any particular skill she may have with words. 
Vendler also contrasts the permeating femaleness of Dickinson's portrayal of nature and nature's emissary with the maleness of Jehovah, Jesus, and all the prophets and apostles that people the Christian tradition and its roots. While God's majesty is awesome (think of his thunderous demands for awe from the suffering and humiliated Job), Nature's majesty is "tender". Her emissary is a quiet woman in Amherst who gardens and bakes bread. Dickinson's "letter" can be contrasted with those of the apostle Paul who wrote letter after letter to early Christians exhorting them, chastising them, and employing arguments based on a rabbinical system of logic and deduction.
Dickinson's nature poetry shows death and rebirth with a daisy; it shows faith with a bee, magnificence with a sunset. Her heavenly saints, like the robins in the trees, make delightful music. 

The letter poem in Dickinson's
hand (with parts of the previous)

Dickinson wrote letters every day, many of them containing poems and many of them mined for poems that are not clearly set out by Dickinson as poems. It is fitting, then, that she uses the device of an informal letter to announce her transcendent role. 

Has she succeeded? Has Dickinson's relay of Nature's "simple news" been read by people she never saw? Have they judged tenderly of her? The answer to both questions is so overwhelmingly "Yes!" that Dickinson, not unaware of her poetic power, would probably be flabbergasted.

I find it interesting, now after 519 poems explicated, that although much of Dickinson's nature poetry is full of rebirth and of almost pantheistic connection, that her religion poetry divides between the somewhat saccharine (saints on streets of gold) and the brutal (God hammering at her soul or allowing the soul to be tortured). Yes, there are nuanced exceptions, but an interesting dichotomy remains. Perhaps the Transcendentalism which took root in New England during her youth attracted her without quite severing the Calvinist Christianity in which she was raised.