Want to search for a every paragraph that has a certain string and return some string from that paragraph

/* ----------------- WANT TO RETURN1 ----------------- */  

machine: some value
server:	WANT TO RETURN1		
owner: some value	 	
notification: some value		
informatica: some value		
sap: some value	
group: This line contains a3 but can have space and characters


/* ----------------- WANT TO RETURN2 ----------------- */

server:	WANT TO RETURN2
machine: some value		
owner: some value	 	
notification: some value		
informatica: some value		
sap: some value	
group:  This line contains a1 but can have space and characters
unix: some value	 	
windows: some value		
aws: some value		
sap1: some value

/* ----------------- WANT TO RETURN3 ----------------- */  


owner: some value
machine: some value		
server:	WANT TO RETURN3	 	
notification: some value		
informatica: some value		
sap: some value	
group: This line contains a1 but can have space and characters


/* ----------------- WANT TO RETURN4 ----------------- */

server:	WANT TO RETURN4
machine: some value		
owner: some value	 	
notification: some value		
informatica: some value		
sap: some value	
group:  This line contains a2 but can have space and characters
unix: some value	 	
windows: some value		
aws: some value		
sap1: some value

Need to do with linux shell script if possible. I have some data in unix file as above. I have a file with multiple values for _STRING_TO_SEARCH_ like job.txt:

a1  
a2  
a3

Example - I want to run a for loop for each value of _STRING_TO_SEARCH_ and capture both _STRING_TO_SEARCH_ and server: value for that paragraph Desired output -

group: a1  
server: WANT TO RETURN2  
server: WANT TO RETURN3

group: a2  
server: WANT TO RETURN4  

group: a3  
server: WANT TO RETURN1

In each paragraph number of rows will vary and fields server: WANT TO RETURN and group:. This line contains a1 but can have space or characters can can occur on any row.