relief... is not the right word

I am having a very hard time thinking of the right word to describe the feeling of being told that the letter that might be the last message you will ever be able to send to someone, has made it across the time and distance, and has been received and read.

it is grateful
it is grieving
it is almost debilitating
it is finished
a part of me can let out the breath it's been holding and rest in peace
and the rest of me celebrates mournfully

I told my brother the good news I'd heard - that his email had been received and read.
"That's good to hear," he said - his shoulders relaxed, bringing his forehead down to his hand as the first tears came, and mine followed.