How to realize batch sending when fishing

0x01 trouble
When making phishing emails , Sometimes there are too many people to send , As a result, too much time is spent in the process of sending emails .

0x02 Solutions

1, The first one can be used as follows , Realize batch sending directly in the recipient , But there is a problem , In this case, batch sending is realized , All recipients' email contents are the same , This can not realize the specialization of everyone's email （ Because you need to add tracker, Through this tracker To track the status of the corresponding message of the corresponding recipient ）, So this method has problems at present .
msg.SetHeader(“Bcc”, mailto…

2, The second is to send directly in parallel , utilize goruntine, Each recipient corresponds to one goruntine. This kind of problem is that you need to set it yourself smtp The number of connections that the server can accept , Ensure client to smtp There are enough connections to correspond to goruntine The number of , Otherwise the connection will reset , Cause unable to send email
As shown below ,activecall Interpretation of parameters
activeCall is an atomic int32; the low bit is whether Close has been called. the rest of the bits are the number of goroutines in Conn.Write.
by 0 when , It means the connection is normal , by 1 when , It means the connection is closed . If smtp The number of connections is less than goruntine The number of , It will cause the connection to close ,activecall Parameter is 1.