Problem Sending Mail From WordPress Using SendGrid

Problem Sending Mail From WordPress Using SendGrid

Hi, I'm having an issue sending mail through WordPress and SendGrid. In the activity log I see the following:

EMAIL: info@twainbow.org
REASON541 5.4.1 Mail rejected by destination domain 
CATEGORY: wp_sendgrid_plugin,
SMTP-ID: < -TMBzusSQUSQOAcf7qRlg@ismtpd0009p1iad1.sendgrid.net>
PROCESSED STRING: December 10, 2017 - 05:39:27 PMMSGID-TMBzusSQUSQOAc-f7qRlg.filter0022p3las1-4232-5A2DC5AD-4B.0
MSGID: -TMBzusSQUSQOAc-f7qRlg.filter0022p3las1-4232-5A2DC5AD-4B.0

Could you help me resolve this issue?