"I have resent your message, I already spoke to him last week". I first thought, OK, he has forwarded the mail.
That is indeed what he meant. This is based on the verb "to resend" (ODO link).
His usage of "to resend" a bit off. It implies that he has sent the message a second time, which is not the case here (the first time, you were the one who sent the message, not him).
A more correct usage would be:
I sent the message. Then I noticed that I sent it without the needed attachment, so I resent the message with the attachment.
I sent it the first time, and then I resent it. It was the same sender both times (me).
Regardless of correctness, what the person who wrote to you meant to say is that he forwarded the message.
But now I have seen that a more formal translation would be "I am angry about your (in some sense annoying) message".
You're thinking of the verb "to resent", which does mean feeling bitter or indignated (ODO link). But this doesn't actually fit in the current sentence:
I have resent your message
Grammatically, this can only be the present perfect tense of "to resend".
There is no grammatically correct interpretation that allows for "to resent" to be used here.
Compare this to other cases in which "to resent" could be grammatically correct:
I resent your message.
This is ambiguous between the two options:
- The present tense of "to resent" => "Today, I am offended by your message"
- The past tense of "to resend" => "Yesterday, I sent your message again"
I have resented your message.
This can only be the present perfect tense of "to resent". But it sounds a bit forced.
I have resentment for your message.
"resentment" is the noun form of "to resent". But it sounds a bit forced, it would be more idiomatic to say that you carry resentment for something.