Gmail API 受使用量限制的约束，该限制会限制 API 方法的调用速率。限额以配额单位（一种表示 Gmail 资源用量的抽象衡量单位）来定义。系统会同时应用两个使用量限制：每个项目的使用量限制和每个用户的使用量限制。下表详细说明了这些使用限额：
| 用量限额类型 | 限制 | 超出原因 |
|---|---|---|
| 每个项目的速率限制 | 每分钟 1,200,000 个配额单位 | rateLimitExceeded |
| 每位用户的速率限制 | 每位用户每分钟 15,000 个配额单位 | userRateLimitExceeded |
每种方法的配额用量
请求消耗的配额单位数因调用的方法而异。下表列出了每种方法的配额单位用量：
| 方法 | 配额单位 |
|---|---|
drafts.create |
10 |
drafts.delete |
10 |
drafts.get |
5 |
drafts.list |
5 |
drafts.send |
100 |
drafts.update |
15 |
getProfile |
1 |
history.list |
2 |
labels.create |
5 |
labels.delete |
5 |
labels.get |
1 |
labels.list |
1 |
labels.update |
5 |
messages.attachments.get |
5 |
messages.batchDelete |
50 |
messages.batchModify |
50 |
messages.delete |
10 |
messages.get |
5 |
messages.import |
25 |
messages.insert |
25 |
messages.list |
5 |
messages.modify |
5 |
messages.send |
100 |
messages.trash |
5 |
messages.untrash |
5 |
settings.delegates.create |
100 |
settings.delegates.delete |
5 |
settings.delegates.get |
1 |
settings.delegates.list |
1 |
settings.filters.create |
5 |
settings.filters.delete |
5 |
settings.filters.get |
1 |
settings.filters.list |
1 |
settings.forwardingAddresses.create |
100 |
settings.forwardingAddresses.delete |
5 |
settings.forwardingAddresses.get |
1 |
settings.forwardingAddresses.list |
1 |
settings.getAutoForwarding |
1 |
settings.getImap |
1 |
settings.getPop |
1 |
settings.getVacation |
1 |
settings.sendAs.create |
100 |
settings.sendAs.delete |
5 |
settings.sendAs.get |
1 |
settings.sendAs.list |
1 |
settings.sendAs.update |
100 |
settings.sendAs.verify |
100 |
settings.updateAutoForwarding |
5 |
settings.updateImap |
5 |
settings.updatePop |
100 |
settings.updateVacation |
5 |
stop |
50 |
threads.delete |
20 |
threads.get |
10 |
threads.list |
10 |
threads.modify |
10 |
threads.trash |
10 |
threads.untrash |
10 |
watch |
100 |