Saving the welcome email is good. Saving the welcome email with the password in plain text is not good. The welcome email should not include the variable {password} by default. It is too easy to overlook when doing the initial Blesta setup.
IMHO - It would be better to archive any emails older than 6 months or a year rather then have the database grow huge.
100 clients getting an average of 2 emails or more per month is 2400 or more emails in the database over the course of 1 year. The emails are stored in plain text. That personal information could be a gold mind if the database got hacked.
Time for some individual encryption, But, can only the mail be encrypted in the DB without having to encrypt the entire sql> ?