id - message - sender - receiver
1  -  hello  -   1    -    2
2  -  hello  -   1    -    2
3  -  hello  -   2    -    1
4  -  hello  -   3    -    1
5  -  hello  -   1    -    3
6  -  hello  -   23   -    1
7  -  hello  -   1    -    23
8  -  hello  -   1    -    2

id   -   name   -       email     -   phone
1    -   abc1   -   abc@gmail.com - 1234567890
2    -   abc2   -   abc@gmail.com - 1234567890
3    -   abc3   -   abc@gmail.com - 1234567890
23   -  abc23   -   abc@gmail.com - 1234567890

SELECT * FROM messages INNER JOIN users ON messages.sender=users.id OR messages.receiver=users.id WHERE users.id!='1' GROUP BY users.id