When using Gmail on Apple's mail, the conversations/threads are not being grouped properly when the subject field of the messages starts having many prefixes "RES" in the subject.

Some email clients (e.g. Mail in iPad), adds a "RE:" or "RES:" prefix every time when a message is replied. This, causes some subject fields having something like: "RES: RES: RES: RES: Original Subject".

When this situation happens, the conversations in Mail.app apparently break, that is, one email (or more) that should be grouped to a conversation is displayed as a different conversation.

This is an example that causes problem for me:

  1. I send a message with subject "Test"
  2. I receive a reply with subject (sent from other email client) "RES: Test"
  3. I reply again (using Mail), then the subject becomes: "Re: RES: Test"
  4. I receive a reply with subject (sent from other email client), and the subject now comes as: "RES: RES: Test"

At this point, I've got 3 different conversations where this should be grouped as one. If I open Gmail, the conversation works perfectly, but in Mail it doesn't. Is there anything I can do about it?

Using Mail.app 6.5

  • Please add within your question which client is in in a Portuguese environment, and which isn't.
    – dan
    Commented Dec 3, 2015 at 13:30

2 Answers 2


The threading does happen based on subject. Re: is ignored; so Re: Re: Re: foo is the same as foo, and the same as Re: Re: foo. That's why it works.

What is RES:? Is it Re: in a different language? That's why it's breaking - because RES is not being ignored and therefore looks like a different subject.

The person you're conversing with needs to use Re:, not RES:. RES: may be inserted automatically by their email client; in which case you may need to find a different way to group the emails, perhaps by sender.

There are tools that can help, though. With MailTags (http://www.indev.ca/MailTags.html) you can group/organize your email much differently or simply use the subject renaming feature. With MailActOn (http://www.indev.ca/MailActOn.html) you can match a rule that moves the email to a specific folder ignoring the "RES" part, etc. There are many options.

No, I am not affiliated with Indev, I just use and love their products. :-) Best of luck.

  • RES: is an abbreviation of reply in Portuguese.
    – Claytinho
    Commented Sep 17, 2013 at 22:41

"RES: " isn't the correct E-mail subject abbreviation in Portuguese.

The correct one is: "RE: " (= Reposta), as documented on Wikipedia: list of Email subject abbreviations → Portuguese.

Fix the E-mail client which is providing you with this wrong field. No E-mail client configured to work with a Portuguese environment will understand it.

  • Unfortunately we can't just "fix the e-mail client which is providing the wrong field". The e-mail client in this case (using "RES:" instead of "RE:") is Microsoft Outlook for Windows and is used by thousands of companies speaking Portuguese. Again, this is perfectly handled by Gmail. Commented Sep 28, 2017 at 15:23

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .