使用Java Mail通过GMail发信的时候出现了如下错误：
550 5.4.5 Daily sending quota exceeded. n37sm954097wag
com.sun.mail.smtp.SMTPSendFailedException: 550 5.4.5 Daily sending quota exceeded. n37sm954097wag
查询了一些资料之后发现是由于：https://mail.google.com/support/bin/answer.py?answer=22839
Are there limits for sending mail?
Gmail has a number of sending limits in place to prevent abuse of our system, and to help fight spam. If you reach one of Gmail’s limits, you’ll be temporarily unable to send mail. This limit is generally removed within 24 hours.
Causes include, but are not limited to:
- Sending a message to more than 500 recipients.
You can send a single message to a maximum of 500 recipients through the web interface, or up to 100 recipients when using POP access. Their email addresses can be distributed among the To, Cc, and Bcc fields. If you communicate with the same group of people on a regular basis, you might be interested in Google Groups.
- Sending a large number of undeliverable messages.
We suggest verifying your contacts’ email addresses. Make sure the email addresses you’re sending mail to are valid. It’s also important that everyone you are sending mail to is willing to receive it.
在另一份文档里Google说Gmail的限制包括上面这些，但绝不仅限于这些。真是挺奇怪。Gmail总是有一些自作聪明的做法