Specific user is not able to send email in suitecrm with OAuth Configuration

I have configured both outbound and inbound emails for a particular user.
but the user can’t able to send an email from email module compose section.

i have configured the multiple outbound emails to that user still that user can’t send an email response error log is

VM38600:1 Uncaught SyntaxError: Unexpected token ‘<’, "<!DOCTYPE "... is not valid JSON at JSON.parse ()
at Object. (EmailsComposeView.js?v=4PKVqT6bQ_GeIFfEGv6MQQ:611:25)
at c (sugar_grp1_jquery.js?v=4PKVqT6bQ_GeIFfEGv6MQQ:2:28327)
at Object.fireWith [as resolveWith] (sugar_grp1_jquery.js?v=4PKVqT6bQ_GeIFfEGv6MQQ:2:29072)
at l (sugar_grp1_jquery.js?v=4PKVqT6bQ_GeIFfEGv6MQQ:2:79901)
at XMLHttpRequest. (sugar_grp1_jquery.js?v=4PKVqT6bQ_GeIFfEGv6MQQ:2:82355)

attaching screenshots for the reference

do you have any custom code injecting JS?