Yahoo Inc / SMTP error code 421
smtp;421 4.7.0 [TSS04] Messages from 0.0.0.0 temporarily deferred due to unexpected volume or user complaints - 4.16.55.1; see https://postmaster.yahooinc.com/error-codes
High severity
This could indicate one of few problems, either that your emails are generating an excessive amount of complaints from Yahoo users or Yahoo is seeing unsual traffic patterns from your mail servers. It could also mean that your email content contains objectionable content or show characteristics indicative of spam. Another possiblity is that your IP has a poor reputation
▓▓▓▓▓▓▓▓▓█▒▓█░░▓░▒▒▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▒▒██░▓▓▓▓▓▓▓▓▓░▒█░▓▓▓▓▓▓▓▓▓▒░░▓█░░░▓▓▓▓▓▓▓▓▓█▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓░▓▓▓▓▓▓▓▓▓▓█▓▓▓▓▓▓▓▓▓░░▒▓▓▓▓▓▓▓▓▓▓░▒░▒▓▒▒█▒░█▓▒▓▒▓▒▒▒█▒▓▓▓▓▓▓▓▓▓▓░░▒▓▒░█▒░▒▒▓▒░░█▓▓░▒▒▒▓▓▒▒█▓▓█▓▒░▓▓▓▓▓▓▓▓▓▒▓▓▓▓▓▓▓▓▓▒▒█▒▒▒▓█▓▓▓▓▓▓▓▓▓▓░▓▓▓▓▓▓▓▓▓▒█▒░▒██▓▓▓▓▓▓▓▓▓▒▒█▒▓▓▓▓▓▓▓▓▓▒▒░▒█░▒░▓▓▓▓▓▓▓▓▓█░▒▒░░░▓█▒▓▓▒▓░▓▓▓▓▓▓▓▓▓█░░█▓▓▓▓▓▓▓▓▓█▒▓▓▓▓▓▓▓▓▓░▒▓▓░▓▓▓▓▓▓▓▓▓▒░▒▓▓▓▓▓▓▓▓▓░▒░▓▒░▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▒█▓███▓▓█▓▓▓▓▓▓▓▓▓▓▒▒▓▓▓▓▓▓▓▓▓▒▒▒▓▓▓▓▓▓▓▓▓░▓░▒▒▓▒▓▓▓▓▓▓▓▓▓▓░░▓░▒▒▓▓▒▓▒▒▒▓▓▓▓▓▓▓▓▓▒▒░▒▒▒▒▒▓▒▓▓▓▓▓▓▓▓▓▒░▒█▒▒▒▓▒░▓█░░▒▒▒▓▓▓▓▓▓▓▓▓▓░█▒▓▓▓▓▓▓▓▓▓▓░▓▒▒▒▒░▒▒▒▒█▒█▓▒▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓░▓█▓▒░▓▓▓▓▓▓▓▓▓█░▓▓▒▒▒▓▓▓▓▓▓▓▓▓▓▓█░▓▒▒▒░▒▓▒░▒▒▓▒▒▒▒░░░▒▒░▒░▒▓▓▓▓▓▓▓▓▓█▒▓▓▓▓▓▓▓▓▓▓▓░▒▒░▒▓▓▓▓▓▓▓▓▓▒▓░█▓▓░███▓▒▓▒░▒█▓▓▓▓▓▓▓▓▓░▒▓█░░▓▓▓▓▓▓▓▓▓▓░▒▒█▒▒█▒▒▒▓▓▓▓▓▓▓▓▓▒░▓▒░▒███░▒▒░▒█▓▓▓▓▓▓▓▓▓▒▒░▒░█▒▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▒▓░▓▓█░▒░░▒▓▒▒░▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▒▓▓▓▓▓▓▓▓▓▒▒▓▓▓▓▓▓▓▓▓▒▒▓██░░▓▓▓▓▓▓▓▓▓▒▓░▓▒░▓▓▓▓▓▓▓▓▓▓▒█▒▓▒▒░▓▓▓▓▓▓▓▓▓░▒▒░▒▒░█▓░▓▓▓▓▓▓▓▓▓▓█░▒██░▓▒▓▓▓▓▓▓▓▓▓▒▓▒▓▓▒▓▓▓▓▓▓▓▓▓▓▒▒▓▓▓▓▓▓▓▓▓▓▓█░▓▓▓▓▓▓▓▓▓░▓▓▒▓▓▓▓▓▓▓▓▓░▒▓░░▓▓▓▓▓▓▓▓▓▒▒░▒░░▒▓