The LogiCommerce tool lets you send a lot of emails simultaneously, but mail servers often do not support such practices as part of their anti-spam control procedures. If a certain quantity is exceeded then mail services may identify your domain email as potential spam. So the answer is to be moderate when sending out many emails. Try not to send more than 300 at the same time (more or less).
If your mail domain is considered to be a spammer, some servers can add that domain to spam lists. If this happens it can severely damage your ability to send and receive mail from that domain.
To check if a mail domain is on a spam list, you can use this tool http://mxtoolbox.com/