Check your synchronization status in User settings

Check the email address of the contact and the email address in the email message

It happens once and a while the email address saved in Tamago-DB is slightly different than the one used to email the contact through your mailbox. It might contain a dot, hyphen, underscore or a character might have been misread : o and 0, i and l, ...

For example, Gmail ignore dots in the email address : 

If someone accidentally adds dots to your address when emailing you, you'll still get that email. For example, if your email is, you own all dotted versions of your address:


Source :

Provider specific troubleshooting