How to Create Powerful, Customized Lua Mailers in HAProxy

blog20230718-01.cfg

global
   lua-load /path/to/file/mailers.lua

blog20230718-02.cfg

mailers smtp_servers
  mailer mailserver1 mailserver1.example.com:25

blog20230718-03.cfg

global
    lua-load /path/to/file/mailers.lua

mailers mymailers
    mailer smtp1 192.168.0.1:587
    mailer smtp2 192.168.0.2:587

backend myback
    email-alert mailers mymailers
    email-alert from test1@domain.name
    email-alert to test2@domain.name
    # add your own monitored backend server entries below

blog20230718-04.lua

-- prepare email body
c:add(string.format("From: %s\r\n", job.mailconf.smtp_from))
c:add(string.format("To: %s\r\n", job.mailconf.smtp_to))
c:add(string.format("Date: %s\r\n", date))
c:add(string.format("Subject: [HAProxy Alert] %s\r\n", job.msg))
c:add("\r\n")
c:add(string.format("%s\r\n", job.msg))