Can I use a single login for multiple instances of Atlassian products?

[Mouse Reusch]

I am running into a situation where I will have a seat on multiple instances of Atlassian (each having Jira Software and some plug-ins, specifically Atlas CRM for Jira).  This is because Atlas CRM does not have an API so that Exalate can sync it across multiple instances.  Can I access multiple Atlassian sites (e.g. FIRST.atlassian.net and SECOND.atlassian.net) using a single email login?  

thanks in advance for any help & advice! cheers, Mouse 

[Hernan Halabi - Elite IT Consulting Group]

Hello @Mouse Reusch the answer would be yes if all instances use the same login method. By default they use Atlassian ID and that one works great for what you ask. Anyway, if one of the environments uses another method like ldap via Atlassian access, that wouldn't work so seamless since even though it might be the same email the authentication method changes.