First, look for Emails in the Spam and Trash mail.
Second, whitelist OTCBTC in your Email server. (Ex: Gmail)
Step 1: Login your Gmail and click the settings above.
Step 2: Click "Filters and Blocked Addresses" and then click "Create a new filter".
Step 3: Enter "@otcbtc.com" and click "Create filter with this search".
Step 4: Select "Never send it to Spam" and click "Create filter".
The filter was created. Please try to send an email again.