I setting `main.cf` in postfix on Linux SUSE like this

```
inet_interfaces = localhost
inet_protocols = ipv4

masquerade_domains =
masquerade_exceptions = root
mydestination = $myhostname, localhost.$mydomain
myhostname = localhost
mynetworks_style = subnet
relayhost=[smtp-relay.gmail.com]:25

smtpd_delay_reject = yes
smtpd_helo_required = no

smtpd_client_restrictions =

smtpd_helo_restrictions =

smtp_sasl_auth_enable = no
smtp_sasl_security_options =
smtp_sasl_password_maps =
smtpd_sasl_auth_enable = no

smtp_use_tls = no

```

I tried to `telnet smtp-relay.gmail.com 25` and it's working

Anyway, when I tried to send email with postfix in server I got the issue.

```
root@localhost
(host smtp-relay.gmail.com[ipv4] refused to talk to me: 421 4.7.0 Try again later, closing connection. (EHLO)

```