This string is the spammiest possible email you can get.
A typical spam threshold triggers at a score of 5.
GTUBE (Generic Test for Unsolicited Bulk Email) tests at 1000.
It's so, unbelievably strong, putting it in your email can ruin your sender score permanently.
I’m genuinely cautious of posting the uncensored string even in image form; for fear of OCR picking it up.
Of course, it’s just a hardcoded test for spam filters.
The architecture of the string itself is actually somewhat interesting:
First of all, it’s what you’d call “7-bit ASCII Clean”.
Every modern character encoding agrees on the first 127 characters.
Even if an old mail server converted character formats, the byte sequence would remain the same.
Many 90s systems strip out the 8th bit!
Jan 13, 2026 18:10The prefix (XJS*) and suffix are particularly high entropy, with the middle being low.
The probability of a human accidentally typing the full string is essentially zero.
This lets us discuss the concept of GTUBE (partial string) without triggering the test itself.
What’s funny is, if your reputation score is super high (think 10+ year domain, perfect DMARC), GTUBE can fail.
Modern filters will *sometimes* give you the benefit of the doubt if you accidentally pull the pin on the grenade.
Still, I wouldn’t mess with it myself!
