The rule of the relations with other sims are: each day the sim lose 2 points in current relation, and in life time relation.
If you use the Insim to be friend with all the hood sims, it's logical, that after 5-6 days he will lose the friendship with all of them, and you will get the amount of messages as the amount of sims he befriended, in this case - about 500...

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Better use the Quick realtions, and befriend only visitors and sims you meet.
Now use the SimPe, and max relations (100/100) with the befriended sims. Do it each 4-5 sim days in the lot you are playing.
For instance, I enter a lot, knowing that my sim is best friend with 25 sims. I play there 3-4 days, may be become friend of another 2-3 sims, then I save the game, exit, open the SimPe, and increase the relations back to 100/100.
You have to download the SimPe version, compatible with the EPs you have.