What is a good way to close an email in Spanish? I need something equal to closing with Best, in English to write back to a Spanish speaking colleague.
I think it would be good to complete this for other possible readers.
Very formal, usually only used in cases where the email/letter will (or can) be used legally or to customers, providers, etc:
Sin otro particular, atentamente,
Same case when you expect a response:
Sin otro particular y a la espera de sus noticias, atentamente,
In that case you can also use "a la espera de sus prontas noticias" if you want to "suggest" urgency without being impolite.
The form "Sin otro particular" is just a formality to indicate you have finished writing, and "atentamente" is the closing. In other Spanish speaking countries (I'm from Spain), you could find other forms for both of them, but the basics in a formal email/letter are in this order: end of the email, closing, name.
The forms proposed by Zero Point in the comments, "Un cordial saludo" and "Reciba un cordial saludo", are equally valid as greetings but just a bit less formal. A good example could be a letter to a customer where you want to seem a bit closer but still being formal.
Reciba un cordial saludo,
If you think you can be less formal, you can just omit the end of the email part, that is the "Sin otro particular" form.
Note that to use both "Sin otro particular" and "(reciba) un cordial saludo" can sound a bit bizarre to a Spanish speaker. It's just too long. So, even when you can use it, commonly that form is only used in less formal writings and, again, omitting the "Sin otro particular".
In even less formal cases like letters to colleagues, internet forums, etc., you can use "Saludos", which is almost the direct translation of Greetings, by the way.
You can even omit your name in that case if you are sure the reader knows who you are.
Also note that at this point, the end of the letter has just disappeared, and it's not returning. The only really necessary part is the greetings part.
And finally, to family, friends, partners (sorry, I'm not sure if this word is right in English, I'm referring to girlfriends/boyfriends), people really close to you, just use "Un abrazo" (hug) or "Besos" (kisses), with all the affectionate, overly sweet or romantic words you'll want to add depending on the relationship.
Abrazos y besos a ti y a los tuyos,
Personally, in Peru, when we talk between work colleagues who are from very different areas (and thus don't know each other), I've seen a lot of people say:
Fname Lname... Rest of the signature
One thing I've seen from an area that deals with particularly high profile clients is
Between people on the same team, a simple "¡Gracias!" is enough. For simple emails, many times we don't even put a closer. I think this question depends a lot more on the countries (and cultures) rather than being a language-specific topic.