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config setprop qmail concurrencyremote 5
That's incorrect, it has wrong capitalisation, it should read:
config setprop qmail ConcurrencyRemote 5
and
config setprop qmail ConcurrencyLocal 10
Taken from previous posts.
Be careful what you take from previous posts.
Those settings do not have a default db entry, but they do have a default value which is used when there is no db entry, as determined by the code in the templates.
To reset to default values just do:
config delprop qmail ConcurrencyRemote
config delprop qmail ConcurrencyLocal
signal-event email-update
PS With only 60K of outgoing bandwidth I'd be setting that to 1 ie
config setprop qmail ConcurrencyRemote 1
signal-event email-update