Just done a test on my server sending to 10 randomly generated recipients, so there is no spam panic, I created a catch all account on my server...

Here are the results I got :

SMTP -> FROM SERVER:220 <my server> ESMTP Postfix (Ubuntu)
SMTP -> FROM SERVER: 250-<my server> 250-PIPELINING 250-SIZE 10240000 250-VRFY 250-ETRN 250-AUTH LOGIN PLAIN 250-AUTH=LOGIN PLAIN 250-ENHANCEDSTATUSCODES 250-8BITMIME 250-DSN 250 STARTTLS
SMTP -> FROM SERVER:250 2.1.0 Ok
SMTP -> FROM SERVER:250 2.1.5 Ok
SMTP -> FROM SERVER:354 End data with .
SMTP -> FROM SERVER:250 2.0.0 Ok: queued as D8AEA80A6EA

Sent individual email to no-one in particular in 0.71606993675232 secondsSMTP -> FROM SERVER:250 2.1.0 Ok
SMTP -> FROM SERVER:250 2.1.5 Ok
SMTP -> FROM SERVER:354 End data with .
SMTP -> FROM SERVER:250 2.0.0 Ok: queued as 1E4F280A6EA

Sent individual email to no-one in particular in 0.21711301803589 secondsSMTP -> FROM SERVER:250 2.1.0 Ok
SMTP -> FROM SERVER:250 2.1.5 Ok
SMTP -> FROM SERVER:354 End data with .
SMTP -> FROM SERVER:250 2.0.0 Ok: queued as 66E2280A6EA

Sent individual email to no-one in particular in 0.36099696159363 secondsSMTP -> FROM SERVER:250 2.1.0 Ok
SMTP -> FROM SERVER:250 2.1.5 Ok
SMTP -> FROM SERVER:354 End data with .
SMTP -> FROM SERVER:250 2.0.0 Ok: queued as AB6AC80A6EA

Sent individual email to no-one in particular in 0.22245907783508 secondsSMTP -> FROM SERVER:250 2.1.0 Ok
SMTP -> FROM SERVER:250 2.1.5 Ok
SMTP -> FROM SERVER:354 End data with .
SMTP -> FROM SERVER:250 2.0.0 Ok: queued as E188480A6EA

Sent individual email to no-one in particular in 0.47082090377808 secondsSMTP -> FROM SERVER:250 2.1.0 Ok
SMTP -> FROM SERVER:250 2.1.5 Ok
SMTP -> FROM SERVER:354 End data with .
SMTP -> FROM SERVER:250 2.0.0 Ok: queued as 607B980A6EA

Sent individual email to no-one in particular in 0.24503397941589 secondsSMTP -> FROM SERVER:250 2.1.0 Ok
SMTP -> FROM SERVER:250 2.1.5 Ok
SMTP -> FROM SERVER:354 End data with .
SMTP -> FROM SERVER:250 2.0.0 Ok: queued as 9C14280A6EA

Sent individual email to no-one in particular in 0.22583603858948 secondsSMTP -> FROM SERVER:250 2.1.0 Ok
SMTP -> FROM SERVER:250 2.1.5 Ok
SMTP -> FROM SERVER:354 End data with .
SMTP -> FROM SERVER:250 2.0.0 Ok: queued as D354180A6EA

Sent individual email to no-one in particular in 0.21672320365906 secondsSMTP -> FROM SERVER:250 2.1.0 Ok
SMTP -> FROM SERVER:250 2.1.5 Ok
SMTP -> FROM SERVER:354 End data with .
SMTP -> FROM SERVER:250 2.0.0 Ok: queued as 141F980A6EA

Sent individual email to no-one in particular in 0.21599817276001 secondsSMTP -> FROM SERVER:250 2.1.0 Ok
SMTP -> FROM SERVER:250 2.1.5 Ok
SMTP -> FROM SERVER:354 End data with .
SMTP -> FROM SERVER:250 2.0.0 Ok: queued as 48F9380A6EA

Sent individual email to no-one in particular in 0.21703791618347 secondsSMTP -> FROM SERVER:250 2.1.0 Ok
SMTP -> FROM SERVER:250 2.1.5 Ok
SMTP -> FROM SERVER:354 End data with .
SMTP -> FROM SERVER:250 2.0.0 Ok: queued as 7DFEF80A6EA

Sent individual email to no-one in particular in 0.21655082702637 secondsSMTP -> FROM SERVER:250 2.1.0 Ok
SMTP -> FROM SERVER:250 2.1.5 Ok
SMTP -> FROM SERVER:354 End data with .
SMTP -> FROM SERVER:250 2.0.0 Ok: queued as B29E680A6EA

Sent individual email to no-one in particular in 0.2194459438324 secondsSMTP -> FROM SERVER:250 2.1.0 Ok
SMTP -> FROM SERVER:250 2.1.5 Ok
SMTP -> FROM SERVER:354 End data with .
SMTP -> FROM SERVER:250 2.0.0 Ok: queued as E88C480A6EA

Sent individual email to no-one in particular in 0.22255706787109 secondsSMTP -> FROM SERVER:250 2.1.0 Ok
SMTP -> FROM SERVER:250 2.1.5 Ok
SMTP -> FROM SERVER:354 End data with .
SMTP -> FROM SERVER:250 2.0.0 Ok: queued as 2A70D80A6EA

Sent individual email to no-one in particular in 0.2162709236145 secondsSMTP -> FROM SERVER:250 2.1.0 Ok
SMTP -> FROM SERVER:250 2.1.5 Ok
SMTP -> FROM SERVER:354 End data with .
SMTP -> FROM SERVER:250 2.0.0 Ok: queued as 5F91A80A6EA

Sent individual email to no-one in particular in 0.22007513046265 secondsSMTP -> FROM SERVER:250 2.1.0 Ok
SMTP -> FROM SERVER:250 2.1.5 Ok
SMTP -> FROM SERVER:354 End data with .
SMTP -> FROM SERVER:250 2.0.0 Ok: queued as 965B780A6EA

Sent individual email to no-one in particular in 0.24743604660034 secondsSMTP -> FROM SERVER:250 2.1.0 Ok
SMTP -> FROM SERVER:250 2.1.5 Ok
SMTP -> FROM SERVER:354 End data with .
SMTP -> FROM SERVER:250 2.0.0 Ok: queued as D1D4780A6FD

Sent individual email to no-one in particular in 0.2244930267334 secondsSMTP -> FROM SERVER:250 2.1.0 Ok
SMTP -> FROM SERVER:250 2.1.5 Ok
SMTP -> FROM SERVER:354 End data with .
SMTP -> FROM SERVER:250 2.0.0 Ok: queued as 1451480A6EA

Sent individual email to no-one in particular in 0.22491598129272 secondsSMTP -> FROM SERVER:250 2.1.0 Ok
SMTP -> FROM SERVER:250 2.1.5 Ok
SMTP -> FROM SERVER:354 End data with .
SMTP -> FROM SERVER:250 2.0.0 Ok: queued as 4AD3680A6EA

Sent individual email to no-one in particular in 0.22699689865112 secondsSMTP -> FROM SERVER:250 2.1.0 Ok
SMTP -> FROM SERVER:250 2.1.5 Ok
SMTP -> FROM SERVER:354 End data with .
SMTP -> FROM SERVER:250 2.0.0 Ok: queued as 839BF80A6EA

Sent individual email to no-one in particular in 0.23592495918274 seconds
Overall time taken to send individual emails to no-one in particular in 5.3630180358887 seconds

__________________
Thanks... Simon