Postfix slow down sending for some ESPs

in  transport regex:
/@.*hotmail\./ slow:
/@.*live\./ slow:
/@.*msn\./ slow:
/@.*yahoo\./ slow:
/@.*aol\./ slow:
/@.*btinternet\./ slow:
/@.*btopenworld\./ slow:
/@.*talk21\./ slow:

Block specific IP addresses

edit: /etc/postfix/main.cf

smtpd_[client/recipient]_restrictions =
…
check_client_access hash:/etc/postfix/blacklist
…

# [client/recipient] selection depends on whether you use the “everything
under smtpd_recipient_restrictions” style main.cf layout.

create: /etc/postfix/blacklist

…
1.2.3.4 REJECT
4.3.2.1 REJECT
3.2.1.4 REJECT
…

/$ postmap /etc/postfix/blacklist
/$ postfix reload