SMTP AUTH Builder
SMTP Authentication Commands
Build AUTH PLAIN or LOGIN responses locally. Credentials must be ASCII.
The result contains reversible credentials. Do not share it. Inputs and output are cleared when you leave. ASCII credentials only; no SASLprep is performed. Send AUTH only after an authenticated TLS connection is established.
Usage guide & examples
PLAIN combines username and password into one Base64 payload. LOGIN sends them separately after server challenges. Use both only over verified TLS. C: is client input; S: is a server reply. Do not type these prefixes.
Console flow / input example
openssl s_client -connect mail.example.com:587 -starttls smtp -servername mail.example.com -verify_hostname mail.example.com -verify_return_error -crlf -quiet C: EHLO client.example.com S: 250-AUTH PLAIN LOGIN PLAIN C: AUTH PLAIN AHVzZXJAZXhhbXBsZS5jb20AcGFzc3dvcmQ= S: 235 Authentication successful LOGIN C: AUTH LOGIN S: 334 VXNlcm5hbWU6 C: dXNlckBleGFtcGxlLmNvbQ== S: 334 UGFzc3dvcmQ6 C: cGFzc3dvcmQ= S: 235 Authentication successful
Processed locally. No input is uploaded or stored.
Scope
The result contains reversible credentials. Do not share it. Inputs and output are cleared when you leave. ASCII credentials only; no SASLprep is performed.
Send AUTH only after an authenticated TLS connection is established.
Result
Where do I use this result?
After verified TLS, send EHLO and confirm the advertised AUTH mechanisms. For PLAIN, send the generated AUTH line. For LOGIN, send AUTH LOGIN, wait for each 334 challenge, then send the generated username and password lines in order. 235 means success; 535 means authentication failed. Base64 is reversible, not encryption.
SMTP connection guide