Change client ip address

[Riivz]

Hello
I have a web application that uses PHPmailer to send notifications by email. The web application runs in docker. The mail server that I must use has strict policy and allows connection only from docker server public ip address. Every time I try send out a notification PHPmailer uses my docker local ip address as client ip address and I cant connect to server. I get this error:
[php7:notice] [pid 28] [client 172.18.0.2:44866] Connection failed. Error #2: stream_socket_client(): unable to connect to ssl://mailserver:465 (Connection refused)
172.18.0.2 is the docker local ip.
What can I do so PHPmailer uses my public ip address instead of docker local ip address for client ip address?

[Synchro]

PHPMailer doesn't get to choose what IP it connects from; that's set by the wider PHP configuration and the networking config in the container, in particular the default routes. This is outside PHPMailer's control.

Separately, PHPMailer doesn't like single-word hostnames because they are indistinguishable from invalid public hostnames, so you may find it's effective to rename your instance from mailserver to something like mailserver.local, or whatever is workable for your config.

[Riivz]

Thx