AWS SES - Connection time-out on port 25

Hello,

Our AWS account ID is 592296619356. We have a Java based web-application running on an EC2 instance in Mumbai which sends emails through SMTP server at Ireland - email-smtp.eu-west-1.amazonaws.com , port 25 (because SES was not available in Mumbai when this account/application was set up).

The emails were going out fine till recently but now we cannot connect to the SMTP server at all and are getting connection timed out errors.

Exception: com.sun.mail.util.MailConnectException: Couldn't connect to host, port: email-smtp.eu-west-1.amazonaws.com, 25; timeout -1;

I tried all the troubleshooting tips at https://aws.amazon.com/premiumsupport/knowledge-center/smtp-connectivity-timeout-issues-ses/ and I am not able to telnet at all which suggested a network issue?

I tried by disabling firewall, adding outbound port 25 and inbound 1024-65535 in our security-group, network acl etc. but it is still unable to connect.
nmap shows that 25 is open on our ec2 and on the smtp server it shows as 25/tcp filtered smtp.

Could you please point me towards a solution to this issue? (Email is an integral part of our application registration/status etc. and without it a user cannot proceed).

Thanks a lot.