smtping is a command to investigate the smtp server.
$ smtping -s 3 -m 3 -d example.com user1 user2 user3
SMTPING example.com: 10 message data bytes
mail session=2 code=250 time=527 ms
mail session=1 code=250 time=541 ms
mail session=3 code=250 time=545 ms
mail session=2 code=250 time=457 ms
mail session=1 code=250 time=456 ms
mail session=3 code=250 time=459 ms
mail session=2 code=250 time=441 ms
mail session=3 code=250 time=445 ms
mail session=1 code=250 time=473 ms
session number=2 host=aspmx.l.example.com. pipe=true tls=true time=2115 ms
session number=3 host=aspmx.l.example.com. pipe=true tls=true time=2154 ms
session number=1 host=aspmx.l.example.com. pipe=true tls=true time=2161 ms
smtping time=2161 ms
$ smtping -auth -d example.com user
SMTP Address <hostname:port>: smtp.example.com:587
UserName: user@example.com
Password:
SMTPING example.com: 10 message data bytes
mail session=1 code=250 time=1181 ms
session number=1 host=smtp.example.com pipe=true tls=true time=2410 ms
smtping time=2410 ms
Usage: smtping [options] -d to_domain to_user...
-addr string
specify a to smtp address <hostname:port>
-byte int
specify a number of data bytes (default 10)
-d string
specify a to domain
-detail
detailed output
-disable-pipe
disable to pipelining
-auth
enter authentication information
-from string
specify a envelope-from
-h this help
-m int
specify a number of messages to send (default 1)
-s int
specify a number of cocurrent sessions (default 1)
-v show version and exit