Cannot send emails but can receive emails AWS Lightsail server

postfix.service - Postfix Mail Transport Agent
   Loaded: loaded (/usr/lib/systemd/system/postfix.service; enabled; vendor preset: disabled)
   Active: active (running) since Mon 2021-09-13 15:07:05 UTC; 6min ago
  Process: 12241 ExecStop=/usr/sbin/postfix stop (code=exited, status=0/SUCCESS)
  Process: 12254 ExecStart=/usr/sbin/postfix start (code=exited, status=0/SUCCESS)
  Process: 12252 ExecStartPre=/usr/libexec/postfix/chroot-update (code=exited, status=0/SUCCESS)
  Process: 12250 ExecStartPre=/usr/libexec/postfix/aliasesdb (code=exited, status=0/SUCCESS)
 Main PID: 12327 (master)
   CGroup: /system.slice/postfix.service
           ├─12327 /usr/libexec/postfix/master -w
           ├─12328 pickup -l -t fifo -u -o content_filter= -o receive_override_options=no_header_body_checks
           ├─12329 qmgr -l -t fifo -u
           ├─12333 tlsmgr -l -t unix -u
           ├─12840 proxymap -t unix -u
           ├─12841 smtp -t unix -u
           └─13002 bounce -z -n defer -t unix -u

Sep 13 15:08:36 srv1.onlinetuition.lk postfix/smtp[12334]: 324DB876D8E: to=, relay=none, delay=503, delays=413/0.03/90/0, dsn=4.4.1, status=deferred (connect to alt2.gmail-smtp-in.l.google.com[142.250.141.26]:25: Connection timed out)
Sep 13 15:08:36 srv1.onlinetuition.lk postfix/smtp[12332]: connect to alt2.gmail-smtp-in.l.google.com[142.250.141.27]:25: Connection timed out
Sep 13 15:08:36 srv1.onlinetuition.lk postfix/smtp[12332]: 0B11C876D8D: to=, relay=none, delay=636, delays=546/0.03/91/0, dsn=4.4.1, status=deferred (connect to alt2.gmail-smtp-in.l.google.com[142.250.141.27]:25: Connection timed out)
Sep 13 15:12:05 srv1.onlinetuition.lk postfix/qmgr[12329]: 93127876D90: from=, size=594, nrcpt=1 (queue active)
Sep 13 15:12:35 srv1.onlinetuition.lk postfix/smtp[12841]: connect to gmail-smtp-in.l.google.com[142.251.10.27]:25: Connection timed out
Sep 13 15:12:35 srv1.onlinetuition.lk postfix/smtp[12841]: connect to gmail-smtp-in.l.google.com[2404:6800:4003:c02::1b]:25: Network is unreachable
Sep 13 15:13:05 srv1.onlinetuition.lk postfix/smtp[12841]: connect to alt1.gmail-smtp-in.l.google.com[173.194.202.27]:25: Connection timed out
Sep 13 15:13:05 srv1.onlinetuition.lk postfix/smtp[12841]: connect to alt1.gmail-smtp-in.l.google.com[2607:f8b0:400e:c00::1b]:25: Network is unreachable
Sep 13 15:13:35 srv1.onlinetuition.lk postfix/smtp[12841]: connect to alt2.gmail-smtp-in.l.google.com[142.250.141.27]:25: Connection timed out
Sep 13 15:13:35 srv1.onlinetuition.lk postfix/smtp[12841]: 93127876D90: to=, relay=none, delay=555, delays=465/0.03/90/0, dsn=4.4.1, status=deferred (connect to alt2.gmail-smtp-in.l.google.com[142.250.141.27]:25: Connection timed out)

I tried the entire day but couldn't fix this issue. Please help. I have cwp pro version.

try testing your server connection to several different mail servers, example

telnet domain.com 25


in this example it you can't connect 173.194.202.27
connect to alt1.gmail-smtp-in.l.google.com[173.194.202.27]:25: Connection timed out

it could be that your outgoing emails are blocked by your provider.

[root@srv1 centos]# telnet domain.com 25Trying 13.228.112.135...telnet: connect to address 13.228.112.135: Connection timed out


You are correct, telnet can't connect to port 25. I think aws blocked this port from their end, even I add firewall rules it is not working.
I'm tiring to find a way to unblock this. Thank you for the update. 

For the benefit of other users..

AWS blocks outbound traffic on port 25 (SMTP) of all EC2 instances and Lambda functions by default. If you want to send outbound traffic on port 25, you can request for this restriction to be removed.

Even they say EC2 and Lambda functions, Lightsail is also the same. So we have to request them to unblock the port. But they always try to sell the Simple email service. So no point talking to them, but you can try..

https://aws.amazon.com/premiumsupport/knowledge-center/ec2-port-25-throttle/