In zoho, there is no possibility of inserting icons into the subject line like in Google (icons were taken from this site https://mainsms.zendesk.com/hc/ru/articles/115004539063-%D0%98%D0%BA%D0%BE%D0 % BD% D0% BA% D0% B8-% D0% B4% D0% BB% D1% 8F-% D0% B2% D1% 81% D1% 82% D0% B0% D0% B2% D0% BA% D0 % B8-% D0% B2-% D1% 82% D0% B5% D0% BC% D1% 83-% D0% BF% D0% B8% D1% 81% D1% 8C% D0% BC% D0% B0)

During testing, it was revealed that they simply do not appear in the theme. Thanks.