TLDR: Mailgun is no longer an option to be used with Ghost

[Kevin]

Replied here:

Mailgun story, again

If you’re self-hosting you can set the batch size in config to get within your Mailgun limits whilst warming up your account. config.production.json { ... "bulkEmail": { "batchSize": 10 } } Just be sure to increase it over time as your account limits are raised (default and max is 1000) to keep your sending and database tables efficient.