The previous default was 5000 sat/vkB and it was lowered to 1000 sat/vkB on [Oct 13, 2015](https://github.com/bitcoin/bitcoin/commit/9e93640be6c49fa1505ba5c5df8c89210da5a6e4). On that day bitcoin was trading for $255 / BTC. So it was deemed that a relay limit of $0.01275/vkB was too high so it was lowered to $0.00255/vkB. In today’s ($11870) figures that would translate to a `minrelaytxfee` of 0.00000022 sat/vkB.
Since to 0.14.0 release, the `minrelaytxfee` still defaults to 1000 sat/vkB, but it is [recommend in the relnotes](https://github.com/bitcoin/bitcoin/blob/master/doc/release-notes/release-notes-0.14.0.md#minimum-fee-rate-policies) that this limit be completely unset.
> Since the changes in 0.12 to automatically limit the size of the mempool and improve the performance of block creation in mining code it has not been important for relay nodes or miners to set -minrelaytxfee.
> The -minrelaytxfee option continues to exist but is recommended to be left unset.
source: [0.14.0 relnotes](https://github.com/bitcoin/bitcoin/blob/master/doc/release-notes/release-notes-0.14.0.md#minimum-fee-rate-policies)
Unsetting this option (`-minrelaytxfee=0`) will allow lower fee TXNs to make it to the miners. Miners will then have a larger selection of TXNs to choose from. For users concerned about mempool bloat, just set `maxmempool` below it’s default of 300 MB (`-maxmempool=200`). Or you could set `minrelaytxfee` to 11 sat/vkB (`-minrelaytxfee=0.00000011`)
Ultimately, I would think that changing the default in bitcoin-core from 1000 sat/vkB to 100 sat/vkB might be a good move. The mempool has already run dry [6 days this month](https://www.reddit.com/r/Bitcoin/comments/i4u5el/psa_low_fee_txns_still_clear_every_day_from_4am/). No reason not to let the miners continue to mine some super low-fee TXNs if they want to. They control this with `blockmintxfee`
What I would suggest adding to `bitcoin.conf`
For those wanting to be more conservative:
Really anything below 1000 sat/vkB would be better.
* [0.14.0 Relnotes](https://github.com/bitcoin/bitcoin/blob/master/doc/release-notes/release-notes-0.14.0.md#minimum-fee-rate-policies)
* r/Bitcoin Thread: [Low Fee TXNs Still Clear Every Day](https://www.reddit.com/r/Bitcoin/comments/i4u5el/psa_low_fee_txns_still_clear_every_day_from_4am/)
* r/Bitcoin Thread: [Should Bitcoin-Core Consider Lowering the Default minrelaytxfee?](https://www.reddit.com/r/Bitcoin/comments/iax954/should_the_bitcoin_reference_implementation/)
* [github commit 9e93640 (Oct 13, 2015)](https://github.com/bitcoin/bitcoin/commit/9e93640be6c49fa1505ba5c5df8c89210da5a6e4) – Lowering default from 5000 to 1000 sat/vkB