Verbose Mode (-v)

The -v command-line switch tells sendmail to run in verbose mode. In that mode, sendmail prints a blow-by-blow[19] description of all the steps it takes in delivering a mail message. To watch sendmail run in verbose mode, send mail to yourself as you did in Run sendmail by Hand on page 6, but this time add a -v switch:

% /usr/lib/sendmail -v you <sendstuff

The output produced shows that sendmail delivers your mail locally:

you... Connecting to local...
you... Sent

When sendmail forwards mail to another machine over a TCP/IP network, it communicates with that other machine using the SMTP protocol. To see what SMTP looks like, run sendmail again, but this time, instead of using you as the recipient, give sendmail your address on another machine:

% /usr/lib/sendmail -v you@remote.domain <sendstuff

The output produced by this command line will look similar to the following:

you@remote.domain... Connecting to remote.domain via smtp... 220 remote.Domain ESMTP Sendmail 8.14.1/8.14.1 ready at Fri, 14 Dec 2007 06:36:12 −080 0 >>> EHLO here.us.edu 250-remote.domain Hello here.us.edu [123.45.67.89], pleased to meet you 250-ENHANCEDSTATUSCODES 250-8BITMIME 250-SIZE 250-DSN 250-ETRN 250-DELIVERBY 250 HELP >>> MAIL From:<you@here.us.edu> SIZE=4537 250 2.1.0 <you@here.us.edu> ... Sender ok >>> RCPT To:<you@remote.domain> 250 2.1.5 <you@remote.domain> ... Recipient ok >>> DATA 354 Enter mail, end with "." on a line by itself >>> . 250 2.0.0 d9L29Nj20475 Message accepted for delivery ...

Get sendmail, 4th Edition now with O’Reilly online learning.

O’Reilly members experience live online training, plus books, videos, and digital content from 200+ publishers.