How to rotate the subject lines automatically? for ex: {Subject line 1 | Subject line 2 | Subject line 3}

You need to put the following line in your subject line while sending the emails. Where Subject line 1, Subject line 2 and Subject line 3 will be your different-different subject lines.

[RANDOM_CONTENT:Subject line 1|Subject line 2|Subject line 3]

You can put any number of subject line separated by ‘|’

For example:

[RANDOM_CONTENT:Hi|Hey|Hello]