If your host listens on all interfaces for SMTP connections on the SMTP port, then I think you should be able to use the docker default network as all containers are connected to thatand it has the host as gateway. So, configure that as SMTP host and see if any emails are logged by your host email server.
[[email protected] ~]# docker network inspect docker_default
[
{
"Name": "docker_default",
"Id": "5fafb2d2f5a54dde20c82efa23286bf15279052e416bd8dc8fda45bdfff15cdd",
"Created": "2019-05-04T14:09:14.599099535+02:00",
"Scope": "local",
"Driver": "bridge",
"EnableIPv6": false,
"IPAM": {
"Driver": "default",
"Options": null,
"Config": [
{
"Subnet": "172.21.0.0/16",
"Gateway": "172.21.0.1"
}
]
},
"Internal": false,
"Attachable": true,
"Ingress": false,
"ConfigFrom": {
"Network": ""
},
"ConfigOnly": false,
"Containers": {
"069b80e1d32c77c2d6ba0c7aab78e57bfdfc6f3d7c0d0f0c1c1a788f874caadc": {
"Name": "bitwarden-api",
"EndpointID": "1c9e63277f4c0019d7b6555cb93d712aa34a12e7a9955cc4c37c7fd6f2ba39a5",
"MacAddress": "02:42:ac:15:00:04",
"IPv4Address": "172.21.0.4/16",
"IPv6Address": ""
},
"32a41e3daa82bec8fa048345b386e5e2f0b311aae1476b678529afe19c328d4b": {
"Name": "bitwarden-web",
"EndpointID": "a8b6a5850e577b1505a5b5c669d1bc770d78952705f76a98cf22720bf6be2844",
"MacAddress": "02:42:ac:15:00:06",
"IPv4Address": "172.21.0.6/16",
"IPv6Address": ""
},
"3e35b4a3b87e5ef50e81f99f66e3b1373ba1fddf064d1eee319b54b7b91f74f5": {
"Name": "bitwarden-attachments",
"EndpointID": "ba25cb4ac5be94ca4ea7a0fde51f1500bc049f05aac2e25d54da8995748ec5e7",
"MacAddress": "02:42:ac:15:00:02",
"IPv4Address": "172.21.0.2/16",
"IPv6Address": ""
},
"4d4594513b957e07f39ea38146ef5c376d55c749cd1fe58d5da3271f9c939d72": {
"Name": "bitwarden-icons",
"EndpointID": "fd1e44bc660e7abc97d5bf1111218748b938cd3172d92e3bcd63900f295f62e2",
"MacAddress": "02:42:ac:15:00:03",
"IPv4Address": "172.21.0.3/16",
"IPv6Address": ""
},
"583448ef1b01095086918672a52e106ecd96cb634ca3e199e6b599bc81246925": {
"Name": "bitwarden-nginx",
"EndpointID": "71a999881d2ddf8e7cfea8737dbfcb4a43fd371380e18b5f231b03f53a96e305",
"MacAddress": "02:42:ac:15:00:0a",
"IPv4Address": "172.21.0.10/16",
"IPv6Address": ""
},
"61b588cbe5e23d5362f851b391f0fab9f2681a4d6165d04007e99f395d120424": {
"Name": "bitwarden-mssql",
"EndpointID": "0c16ef4bf9ab66aef5f6fadbdbce990925e7cb5795a11143e4815f620e765c1b",
"MacAddress": "02:42:ac:15:00:09",
"IPv4Address": "172.21.0.9/16",
"IPv6Address": ""
},
"69995ab45c119a1e4202ea64c2fbcd554e0e8e519e853957ea71e38c53e95b20": {
"Name": "bitwarden-identity",
"EndpointID": "f8d070d90146db3ed97f99e9ddf59a03b3a7b09a66a099965673e7601408ea1b",
"MacAddress": "02:42:ac:15:00:07",
"IPv4Address": "172.21.0.7/16",
"IPv6Address": ""
},
"809809950b35c123355d34cd3c55357ec010d187b17b3682b3ccd840ecc57ade": {
"Name": "bitwarden-notifications",
"EndpointID": "79a1b57d8860c47578acd4498573a0109793e05d354e6a6836d074c6f5e92403",
"MacAddress": "02:42:ac:15:00:05",
"IPv4Address": "172.21.0.5/16",
"IPv6Address": ""
},
"c0b90132a1d8749894b487c6eed3c9e69320777645935cff28d1f85cceee34f1": {
"Name": "bitwarden-admin",
"EndpointID": "d564c4978dabfb0d09a2ce0a0cc576321cd5a334c782707c460eed94ca915c9e",
"MacAddress": "02:42:ac:15:00:08",
"IPv4Address": "172.21.0.8/16",
"IPv6Address": ""
}
},
"Options": {},
"Labels": {
"com.docker.compose.network": "default",
"com.docker.compose.project": "docker",
"com.docker.compose.version": "1.24.0"
}
}
]
[[email protected] ~]#