It's a problem that exist in every services that relies on emails. I've had my fair share as well, just not in bittrex but in other platforms. What worked for me was trying again after waiting for an hour or two, or less.

But before that, try the first aid

Bittrex: https://bittrex.zendesk.com/hc/en-us/articles/115001324851-Not-receiving-email-from-Bittrex
Bittrex global: https://bittrexglobal.zendesk.com/hc/en-us/articles/360009625040-Not-receiving-email-from-Bittrex-Global

If none worked, proceed to contact bittrex/global and your email provider.

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Meta - Try to start your own thread next time