no, you are wrong. no such 规定.

never hear that 邮件厚度不够，升级成priority mail是邮局的规定,

this is not right. no such 规定.

www.usps.com

First-Class Mail :

First-Class Mail gets your mail there fast.

Postcards, letters, large envelopes (flats) and small packages can be sent using First-Class Mail®. This service, along with Priority Mail and Express Mail, is ideal for sending personal correspondence, handwritten or typewritten letters, and bills or statements of account. It may also be used for advertisements and lightweight merchandise. First-Class Mail prices are based on both the shape and weight of the item being mailed. For items weighing more than 13 ounces, use Priority Mail.

所有跟帖： 

• well, figure out yourself: http://www.usps.com/prices/first-clas -小小爱茉莉- ♀ (54 bytes) () 11/13/2009 postreply 13:58:44

• actually you are completely wrong on this issue -远唯一- ♂ (224 bytes) () 11/13/2009 postreply 14:09:23

• 问题找麻烦的邮局营业员不是找重里的茬，是找邮件体积的荐。 -小小爱茉莉- ♀ (0 bytes) () 11/13/2009 postreply 14:13:55

• you are wrong, if邮件体积is big, you need to use priority mail -远唯一- ♂ (158 bytes) () 11/13/2009 postreply 14:19:14

• 此规定找到了，我很早以前看过 -小小爱茉莉- ♀ (288 bytes) () 11/13/2009 postreply 14:23:19

• 也可以让你的客户把她的local PO电话给你，电话过去问问就清楚了。 -小小爱茉莉- ♀ (0 bytes) () 11/13/2009 postreply 14:03:15

• well, anyway, it is strange -远唯一- ♂ (96 bytes) () 11/13/2009 postreply 14:10:57