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Sending email with sendgrip plugin, blocked by yahoo

Sendgrid account is setup, sender (in Sendgrid) also,
plugin in my app is working well when sending to email address other than or

Logs in bubble: the workflow activate the “send action”
log activity in sendgrid :

and detail for the “not delivered” :

in the yahoo help about error-codes ( Yahoo Error Codes

SO it is not directly a probem with the plugin because it was working at least one time, I cant go on with my app !!!

I would ike to know if somebody has already had this blocking problem ?
Any advice to fix or unlock?

Thank you for the time you’ll take to answer