Fortigate vs outlook android

I am using MDaemon as my Email host behind fortigate 100f. I am able to connect to my mdaemon server using webmail as well as outlook desktop however facing issues with outlook android. I am able to sync imap emails but unable to send email from outlook android. all recommended ports are open and accessible from outside. what could be the reason fortigate blocking outlook android traffic and how can I solve this step by step. urgent response will be appreciated. (Note: All ports are open, SSL configured and working, webmail and outlook desktop working fine even adding accounts in Gmail is working fine).
Only outlook android not sending mail say "error sending mail please try again"