Correct

另函

/ lìng hán / 
Strokes

Example

As a Noun

another letter

1
Lìng
另
hán
函
gàozhī
告知

inform in another letter

As a Verb

write another letter

2
Xiángqíng
详情
lìng
另
hán
函
  
。

I will write you another letter about the details.