Ok, I used the --config None option only because it is suggested in the management section of the forum when celery is not running. Now I have celery running as

flask --config flaskbb.cfg celery worker -E

The e-mails arrive, but still the same error 'Your account activation token is invalid.' The activation link looks like:

http://mydomain.org/auth/activate/eyJpYXQiOjE0OTUxOTM0NTIsImV4cCI6MTQ5NTE5NzA1MiwiYWxnIjoiSFMyNTYifQ.eyJpZCI6OCwib3AiOiJhY3RpdmF0ZV9hY2NvdW50In0.r_D1p00H6KshWPNrDYYCICQ_9ZsPzLe23ZdXWpglQlw

Is flaskbb running with the same 'flaskbb.cfg' config as well?

The link looks ok to me.

I think you meant flaskbb and not flask (the command)?

Yes, I meant flaskbb :-). The config is indeed the one I am running flaskbb with. Do you have any suggestion what might be wrong? The page with the error is loading fine so I suppose my Nginx config is not at fault.

Well, It seems that I might have to do some debugging of the flaskbb code and try to find what is wrong.

Mhh I don't know unfortunately. I have pushed a fix to github which (re)enables you to input the token via the form. Please let me know what caused the error so that I can implement a fix (or you, if you want ;))

have the same problem as described above: I configured celery to work without redis

REDIS_ENABLED = False
REDIS_URL = ""
REDIS_DATABASE = 0

# Celery
# ------------------------------
CELERY_BROKER_URL = ""
CELERY_RESULT_BACKEND = ""

when run flaskbb --config flaskbb.cfg celery worker

celery writes a message:

[2017-06-01 01:13:33,265: ERROR/MainProcess] consumer: Cannot connect to amqp://guest:**@127.0.0.1:5672//: [Errno 111] Connection refused.
Trying again in 2.00 seconds...

maybe it is possible to send emails without headache with celery?

You have configured celery to use it's default (see: http://docs.celeryproject.org/en/latest/userguide/configuration.html#broker-settings) and by default it tries to connect to an amqp server. It is possible to send emails without celery but then you won't be able to send the mails asynchronously.

ps: the demo account is not a support account..

I guess that reason is I configured celery improperly. The question is what parameters should we use to make celery working without redis (if it is possible)? Either it requires some other service instead of redis?
Sorry possible stupid questions but I hever used celery before...