They put limits on stuff, don't know how to get around them. There a lot of tools that will extract but the limits are put on by Gmail and are usually even lowered with other software (as an example you can send a gmail to 500 recipeints in your browser but only 200 in something like outlook - these limits are placed by gmail itself).
Let me know if you find a workaround for their limits, it could probably be altered for sending as well then throw away gmails can be used for sending.