[DanielDent]

"IPv6 support 1. Took forever to implement, and the timetable broke promises to customers. 2. Inferior. Digital Ocean still won't give you a /64 per standards."

Far more egregious is that they silently drop port 25 on IPv6. This means that enabling IPv6 will cause mail problems for some destinations (destinations that support IPv6, like Google). When asked they say it's because a /64 is too much address space in the hands of potential (ab)users. This fails to understand that an IPv6 /64 is conceptually similar to an IPv4 /32. (In fact, there are pretty reasonable arguments for assigning IPv6 /56s or /48s with the same semantics as how IPv4 /32s are assigned.)

[joering2]

I can't talk about port 25, but we have 15 mailservers hosted on $5/per pop with DigitalOcean and with properly setup rDNS and SPF including our IPv6 address, we don't see any problems with deliveribility to gmail via subscription port.

That is on circa 600,000 emails per month sent to gmail.

[DanielDent]

You send server-to-server messages on port 587? That is... non-standard. But an interesting approach.

You are using your users' gmail credentials? Or are you simply delivering over 587 the same as you would over 25?

[jlgaddis]

It's very "non-standard" -- that's not what the submission port (587/TCP) -- not "subscription port" -- is for.

[robertcope]

It sounds like you're talking about sending mail, not receiving it. Port 25 is only an issue if you're trying to receive email.

[mwpmaybe]

If you want to send mail as a peer (i.e. without using a smart host / relay) you need to be able to connect outbound on port 25, which some providers block.