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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, w

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.

robertcope 11y ago
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 11y ago
  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.
DanielDent 11y ago
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 11y ago
  It's very "non-standard" -- that's not what the submission port (587/TCP) -- not "subscription port" -- is for.