╧≡ΦδεµσφΦ 

╧≡ΦδεµσφΦσ 1. ╩ε∞αφΣ√ ∩≡ε≥εΩεδα SMTP

HELO <SP> <domain> <CRLF> ╬≥Ω≡√≥ⁿ ±σ±±Φ■ ΓταΦ∞εΣσΘ±≥ΓΦ  ∩ε ∩≡ε≥εΩεδ≤ SMTP. <domain> - Σε∞σφφεσ Φ∞  ∞α°Φφ√
MAIL <SP> FROM:<reverse-path> <CRLF> ╤εεß∙Φ≥ⁿ αΣ≡σ± ε≥∩≡αΓΦ≥σδ  (<reverse-path>). ╬ß τα≥σδⁿφα  Ωε∞αφΣα, Ωε≥ε≡≤■ φαΣε Γ√Σα≥ⁿ ∩σ≡σΣ ε≥∩≡αΓΩεΘ ±εεß∙σφΦ 
RCPT <SP> TO:<forward-path> <CRLF> ╤εεß∙Φ≥ⁿ αΣ≡σ± ∩εδ≤≈α≥σδ  (forward-path). ╬ß τα≥σδⁿφα  Ωε∞αφΣα, Ωε≥ε≡≤■ Γ√Σα■≥ ∩ε±δσ MAIL FROM, φε ∩σ≡σΣ DATA
DATA <CRLF> ═α≈α≥ⁿ ∩σ≡σΣα≈≤ ≥σδα ∩ε≈≥εΓεπε ±εεß∙σφΦ . ╥σδε ±εεß∙σφΦ  Σεδµφε Ωεφ≈α≥ⁿ±  ≥ε≈Ωε■(".") Γ ∩σ≡ΓεΘ ∩ετΦ÷ΦΦ ±≥≡εΩΦ
RSET <CRLF>
SEND <SP> FROM:<reverse-path> <CRLF> ╧ε±δα≥ⁿ ±εεß∙σφΦσ φα ≥σ≡∞Φφαδ ∩εδⁿτεΓα≥σδ , Ωε≥ε≡√Θ ε∩≡σΣσδ σ≥±  Ωε∞αφΣεΘ RCPT
SOML <SP> FROM:<reverse-path> <CRLF> SEND OR MAIL. ╧ε±δα≥ⁿ Γ ∩ε≈≥εΓ√Θ  ∙ΦΩ ΦδΦ φα ≥σ≡∞Φφαδ ∩εδⁿτεΓα≥σδ 
SAML <SP> FROM:<reverse-path> <CRLF> SEND AND MAIL. ╧ε±δα≥ⁿ Γ ∩ε≈≥εΓ√Θ  ∙ΦΩ Φ φα ≥σ≡∞Φφαδ ∩εδⁿτεΓα≥σδ 
VRFY <SP> <string> <CRLF> ╧εδ≤≈Φ≥ⁿ Φφ⌠ε≡∞α÷Φ■ ε ∩εδⁿτεΓα≥σδσ, Φ∞  Ωε≥ε≡επε ≤Ωατ√Γασ≥±  Γ Ωα≈σ±≥Γσ α≡π≤∞σφ≥α Ωε∞αφΣ√ (<string>)
EXPN <SP> <string> <CRLF> ╧εδ≤≈Φ≥ⁿ Φφ⌠ε≡∞α÷Φ■ ε ∩εδⁿτεΓα≥σδ ⌡ τα≡σπΦ±≥≡Φ≡εΓαφφ√⌡ Γ Ωα≈σ±≥Γσ ∩εδ≤≈α≥σδσΘ Ωε≡≡σ±∩εφΣσφ÷ΦΦ
HELP [<SP> <string>] <CRLF> ╩≡α≥Ωα  ±∩≡αΓΩα ∩ε Ωε∞αφΣα∞ ∩≡ε≥εΩεδα
NOOP <CRLF> ═σ≥ ε∩σ≡α÷ΦΦ
QUIT <CRLF> ╟αΓσ≡°Φ≥ⁿ ±σ±±Φ■
TURN <CRLF> ╧ε∞σφ ≥ⁿ±  ∞σ±≥α∞Φ ±σ≡Γσ≡≤ Φ ΩδΦσφ≥≤

╧≡ΦδεµσφΦσ 2. ╩εΣ√ ΓετΓ≡α≥α SMTP

211System status, or system help reply ╤≥α≥≤± ±Φ±≥σ∞√ ΦδΦ Help
214Help message. [Information on how to use the receiver or the meaning of a particular non-standard command; this reply is useful only to the human user] ╩≡α≥Ωα  ±∩≡αΓΩα
220<domain> Service ready SMTP-±σ≡ΓΦ± πε≥εΓ Ω ≡αßε≥σ
221<domain> Service closing transmission channel ╤σ≡ΓΦ± ταΩ≡√δ Ωαφαδ ∩σ≡σΣα≈Φ Σαφφ√⌡
250Requested mail action okay, completed ╤εσΣΦφσφΦσ ≤±≥αφεΓδσφε
251User not local; will forward to <forward-path> ╧εδⁿτεΓα≥σδⁿ φσ ∞σ±≥φ√Θ. ┬√∩εδφΦ≥ⁿ ∩σ≡σφα∩≡αΓδσφΦσ τα∩≡ε±α
354Start mail input; end with <CRLF>.<CRLF> ═α≈α≥ⁿ ΓΓεΣ ∩ε≈≥εΓεπε ±εεß∙σφΦ 
421<domain> Service not available, closing transmission channel [This may be a reply to any command if the service knows it must shut down] ╤σ≡ΓΦ± ε≥±≤≥±≥Γ≤σ≥. ╩αφαδ ∩σ≡σΣα≈Φ Σαφφ√⌡ ταΩ≡√≥
450Requested mail action not taken: mailbox unavailable [E.g., mailbox busy] ═σ≥ Γετ∞εµφε±≥Φ τα∩Φ±α≥ⁿ Σαφφ√σ Γ ∩ε≈≥εΓ√Θ  ∙ΦΩ
451Requested action aborted: local error in processing ╬°ΦßΩα ∩≡Φ εß≡αßε≥Ωσ τα∩≡ε±α
452Requested action not taken: insufficient system storage ╟α∩≡ε± φσ Γ√∩εδφσφ φσΣε±≥α≥ε≈φε ∩α∞ ≥Φ φα Γ√≈Φ±δΦ≥σδⁿφεΘ ≤±≥αφεΓΩσ
500Syntax error, command unrecognized [This may include errors such as command line too long] ╤Φφ≥αΩ±Φ≈σ±Ωα  ε°ΦßΩα - φσ≥ ≥αΩεΘ Ωε∞αφΣ√
501Syntax error in parameters or arguments ╤Φφ≥αΩ±Φ≈σ±Ωα  ε°ΦßΩα Γ α≡π≤∞σφ≥α⌡ Ωε∞αφΣ√
502Command not implemented ─αφφα  Ωε∞αφΣα φσ ∞εµσ≥ ß√≥ⁿ Γ√∩εδφσφα
503Bad sequence of commands ═σ∩≡αΓΦδⁿφα  ∩ε±δσΣεΓα≥σδⁿφε±≥ⁿ Ωε∞αφΣ
504Command parameter not implemented ╧α≡α∞σ≥≡ Ωε∞αφΣ√ φσ ∞εµσ≥ ß√≥ⁿ Φ±∩εδⁿτεΓαφ Γ Σαφφε∞ Ωεφ≥σΩ±≥σ
550Requested action not taken: mailbox unavailable [E.g., mailbox not found, no access] ═σ φαΘΣσφ ±εε≥Γσ≥±≥Γ≤■∙ΦΘ ∩ε≈≥εΓ√Θ  ∙ΦΩ
551User not local; please try <forward-path> ╧εδⁿτεΓα≥σδⁿ φσ φαΘΣσφ ∞εµφε ∩ε∩≡εßεΓα≥ⁿ ε≥∩≡αΓΦ≥ⁿ ∩ε≈≥≤ ∩ε Σ≡≤πε∞≤ αΣ≡σ±≤
552Requested mail action aborted: exceeded storage allocation ╧≡σΓ√°σφ√ ΩΓε≥√ φα Φ±∩εδⁿτεΓαφΦσ ≡σ±≤≡±εΓ ∩α∞ ≥Φ
553Requested action not taken: mailbox name not allowed [E.g., mailbox syntax incorrect] ╚∞  ∩ε≈≥εΓεπε  ∙ΦΩα φσ∩≡αΓΦδⁿφεσ
554Transaction failed ╬ß∞σφ ταΓσ≡°Φδ±  αΓα≡ΦΘφε

═αταΣ | ╤εΣσ≡µαφΦσ