When I attach a reserved IP to a droplet and route outgoing traffic through it, port 25 (SMTP) isn't allowed. I'd like outgoing SMTP traffic through a reserved IP to be allowed.

The risk I'm mitigating is losing an IP I've built a good email reputation with. I'm still able to run and maintain an email server without this feature; I can rebuild droplets for OS upgrades without losing their original IPs. I do still run the risk of https://ideas.digitalocean.com/network/p/reserve-ip-addresses-make-sure-we-can-keep-an-ip-if-we-recreate-a-droplet if I'm unlucky, though.