> Do you think spammers are too stupid to strip out the + part themselves?
No, but they are only targeting gullible people anyway so they don't bother:
> Finally, this approach suggests an answer to the question ["Why Do Nigerian Scammers Say They are From Nigeria"]? Far-fetched tales of West African riches strike most as comical. Our analysis suggests that is an advantage to the attacker, not a disadvantage. Since his attack has a low density of victims the Nigerian scammer has an over-riding need to reduce false positives. By sending an email that repels all but the most gullible the scammer gets the most promising marks to self-select, and tilts the true to false positive ratio in his favor.
https://www.microsoft.com/en-us/research/publication/why-do-...
