zulip/templates/zerver/emails/macros.html

{% macro email_tag(email, text) -%}
    <a href="mailto:{{ email }}">{{ text | default(email) }}</a>
{%- endmacro %}

{% macro referrer_email_tag(referrer_email, referrer_name) -%}
    <a href="mailto:{{ referrer_email }}">{{ referrer_name }} ({{ referrer_email }})</a>
{%- endmacro %}

{% macro link_tag(url, text) -%}
    <a href="{{ url }}">{{ text | default(url) }}</a>
{%- endmacro %}