Emails once sent have no influence from iCertifi and are down to the server or receiving email address. Your electrical certificate is sent through Apple's email client and your email provider, not iCertifi. First thing to check is if it's being blocked by anti-spam software
Reset device by holding down on the Sleep and Home buttons at the same time for about 10-12 seconds until the Apple Logo appears - ignore the red slider - let go of the buttons. (This is equivalent to rebooting your computer.)
Or this - Delete the account in Mail and then set it up again. Settings->Mail, Contacts, Calendars -> Accounts Tap on the Account, then on the red button that says Remove Account.
Some other things to try:
iOS: Unable to send or receive email
Can’t Send Emails on iPad – Troubleshooting Steps
Setting up and troubleshooting Mail
Using a POP account with multiple devices
iOS: Adding an email account
iOS: Setting up an Outlook.com, Hotmail, Live, or MSN email account
Server does not allow relaying email error, fix
Why Does My iPad Say "Cannot Connect to Server"?
iOS: 'Mailbox Locked', account is in use on another device, or prompt to re-enter POP3 password
Configuration problems with IMAP e-mail on iOS with a non-standard SSL port.
http://colinrobbins.me/2013/02/09/configuration-problems-with-imap-e-mail-on-ios -with-a-non-standard-ssl-port/http://colinrobbins.me/2013/02/09/configuration-problems-with-imap-e-mail-on-ios -with-a-non-standard-ssl-port/
Best Regards and thanks for using iCertifi