I've used a mailbox.org account multiple times to send an identical email to about 500 addresses within a couple hours. Beforehand I checked their support secti

I've used a mailbox.org account multiple times to send an identical email to about 500 addresses within a couple hours. Beforehand I checked their support section and they stated some limits there which seemed to be fine for my purposes, with much higher limits for business plans. Note that this is likely different for the first 30 days as those are considered a testing period (and usually free iirc).